Transmission structures and formats for dl control channels

ABSTRACT

A method for a user equipment (UE) to receive physical downlink control channels (PDCCHs) is provided. The UE receives configuration information for a first control resource set that includes a number of symbols in a time domain and a number of resource blocks (RBs) in a frequency domain, configuration information indicating a first number of Nbundle,1 frequency-contiguous RBs, and a PDCCH in the first control resource set in a number of frequency distributed blocks of Nbundle,1 RBs. The UE assumes that a demodulation reference signal associated with the reception of the PDCCH has a same precoding over the Nbundle,1 RBs. A method for constructing a search space to reduce a number of channel estimations that the UE performs for decoding PDCCHs, relative to conventional search spaces, is also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM OF PRIORITY

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 62/455,155, filed on Feb. 6, 2017; U.S. ProvisionalPatent Application Ser. No. 62/469,616, filed on Mar. 10, 2017; U.S.Provisional Patent Application Ser. No. 62/471,528, filed on Mar. 15,2017; U.S. Provisional Patent Application Ser. No. 62/479,604, filed onMar. 31, 2017; U.S. Provisional Patent Application Ser. No. 62/509,233,filed on May 22, 2017; and U.S. Provisional Patent Application Ser. No.62/580,494, filed on Nov. 2, 2017. The content of the above-identifiedpatent document is incorporated herein by reference.

TECHNICAL FIELD

The present application relates generally to control channels operationin wireless communication systems. More specifically, this disclosurerelates to transmission structures and formats in wireless communicationsystems.

BACKGROUND

5th generation (5G) mobile communications, initial commercialization ofwhich is expected around 2020, is recently gathering increased momentumwith all the worldwide technical activities on the various candidatetechnologies from industry and academia. The candidate enablers for the5G mobile communications include massive antenna technologies, fromlegacy cellular frequency bands up to high frequencies, to providebeamforming gain and support increased capacity, new waveform (e.g., anew radio access technology (RAT)) to flexibly accommodate variousservices/applications with different requirements, new multiple accessschemes to support massive connections, and so on. The InternationalTelecommunication Union (ITU) has categorized the usage scenarios forinternational mobile telecommunications (IMT) for 2020 and beyond into 3main groups such as enhanced mobile broadband, massive machine typecommunications (MTC), and ultra-reliable and low latency communications.In addition, the ITC has specified target requirements such as peak datarates of 20 gigabit per second (Gb/s), user experienced data rates of100 megabit per second (Mb/s), a spectrum efficiency improvement of 3×,support for up to 500 kilometer per hour (km/h) mobility, 1 millisecond(ms) latency, a connection density of 106 devices/km2, a network energyefficiency improvement of 100× and an area traffic capacity of 10Mb/s/m2. While all the requirements need not be met simultaneously, thedesign of 5G networks may provide flexibility to support variousapplications meeting part of the above requirements on a use case basis.

SUMMARY

The present disclosure relates to a pre-5th-Generation (5G) or 5Gcommunication system to be provided for supporting higher data ratesbeyond 4th-Generation (4G) communication system such as long termevolution (LTE). Embodiments of the present disclosure providetransmission structures and format in advanced communication systems.

In one embodiment, a method for a user equipment (UE) to receive aphysical downlink control channel (PDCCH) is provided. The methodcomprises receiving configuration information for a first controlresource set that includes a number of symbols in a time domain and anumber of resource blocks (RBs) in a frequency domain. The method alsocomprises receiving a configuration indicating a first numberN_(bundle,1) of frequency-contiguous RBs. The method additionallycomprises receiving a first PDCCH in the control resource set in anumber of frequency distributed blocks of N_(bundle,1) RBs. The UEassumes that a demodulation reference signal associated with thereception of the first PDCCH has a same precoding over the N_(bundle,1)RBs.

In another embodiment, a user equipment (UE) comprises a receiverconfigured to receive configuration information for a first controlresource set that includes a number of symbols in a time domain and anumber of resource blocks (RBs) in a frequency domain. The receiver isalso configured to receive configuration information indicating a firstnumber N_(bundle,1) of frequency-contiguous RBs. The receiver isadditionally configured to receive a physical downlink control channel(PDCCH) in the control resource set in a number of frequency distributedblocks of N_(bundle,1) RBs. The receiver assumes that a demodulationreference signal associated with the reception of the PDCCH has a sameprecoding over the N_(bundle,1) RBs.

In yet another embodiment, a base station comprises a transmitterconfigured to transmit configuration information for a first controlresource set that includes a number of symbols in a time domain and anumber of resource blocks (RBs) in a frequency domain. The transmitteris also configured to transmit configuration information indicating afirst number N_(bundle,1) of frequency-contiguous RBs. The transmitteris additionally configured to transmit a physical downlink controlchannel (PDCCH) in the control resource set in a number of frequencydistributed blocks of N_(bundle,1) RBs. A demodulation reference signalassociated with the transmission of the PDCCH has a same precoding overthe N_(bundle,1) RBs.

Other technical features may be readily apparent to one skilled in theart from the following figures, descriptions, and claims.

Before undertaking the DETAILED DESCRIPTION below, it may beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document. The term “couple” and its derivativesrefer to any direct or indirect communication between two or moreelements, whether or not those elements are in physical contact with oneanother. The terms “transmit,” “receive,” and “communicate,” as well asderivatives thereof, encompass both direct and indirect communication.The terms “include” and “comprise,” as well as derivatives thereof, meaninclusion without limitation. The term “or” is inclusive, meaningand/or. The phrase “associated with,” as well as derivatives thereof,means to include, be included within, interconnect with, contain, becontained within, connect to or with, couple to or with, be communicablewith, cooperate with, interleave, juxtapose, be proximate to, be boundto or with, have, have a property of, have a relationship to or with, orthe like. The term “controller” means any device, system or part thereofthat controls at least one operation. Such a controller may beimplemented in hardware or a combination of hardware and software and/orfirmware. The functionality associated with any particular controllermay be centralized or distributed, whether locally or remotely. Thephrase “at least one of,” when used with a list of items, means thatdifferent combinations of one or more of the listed items may be used,and only one item in the list may be needed. For example, “at least oneof: A, B, and C” includes any of the following combinations: A, B, C, Aand B, A and C, B and C, and A and B and C.

Moreover, various functions described below can be implemented orsupported by one or more computer programs, each of which is formed fromcomputer readable program code and embodied in a computer readablemedium. The terms “application” and “program” refer to one or morecomputer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitable computerreadable program code. The phrase “computer readable program code”includes any type of computer code, including source code, object code,and executable code. The phrase “computer readable medium” includes anytype of medium capable of being accessed by a computer, such as readonly memory (ROM), random access memory (RAM), a hard disk drive, acompact disc (CD), a digital video disc (DVD), or any other type ofmemory. A “non-transitory” computer readable medium excludes wired,wireless, optical, or other communication links that transporttransitory electrical or other signals. A non-transitory computerreadable medium includes media where data can be permanently stored andmedia where data can be stored and later overwritten, such as arewritable optical disc or an erasable memory device.

Definitions for other certain words and phrases are provided throughoutthis patent document. Those of ordinary skill in the art shouldunderstand that in many if not most instances, such definitions apply toprior as well as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 illustrates an example wireless network according to embodimentsof the present disclosure;

FIG. 2 illustrates an example eNB according to embodiments of thepresent disclosure;

FIG. 3 illustrates an example UE according to embodiments of the presentdisclosure;

FIG. 4 illustrates an example DL slot structure for PDSCH transmissionor PDCCH transmission according to embodiments of the presentdisclosure;

FIG. 5 illustrates an example UL slot structure for PUSCH transmissionor PUCCH transmission according to embodiments of the presentdisclosure;

FIG. 6 illustrates an example hybrid slot structure for DL transmissionsand UL transmissions according to embodiments of the present disclosure;

FIG. 7 illustrates an example transmitter structure using OFDM accordingto embodiments of the present disclosure;

FIG. 8 illustrates an example receiver structure using OFDM according toembodiments of the present disclosure;

FIG. 9 illustrates an example encoding process for a DCI formataccording to embodiments of the present disclosure;

FIG. 10 illustrates an example decoding process for a DCI format for usewith a UE according to embodiments of the present disclosure;

FIG. 11 illustrates an example distributed PDCCH transmission structuredepending on a respective CCE aggregation level according to embodimentsof the present disclosure;

FIG. 12 illustrates an example localized PDCCH transmission structuredepending on a respective CCE aggregation level according to embodimentsof the present disclosure;

FIG. 13 illustrates an example PDCCH transmission and PDSCH transmissionusing a same DMRS for demodulation according to embodiments of thepresent disclosure;

FIG. 14 illustrates an example operation for a UE to assume a same DMRSprecoding in predetermined slots and in predetermined RBs of a DLcontrol resource set according to embodiments of the present disclosure;

FIG. 15 illustrates an example operation for a DCI format that include abinary flag to indicate a transmission scheme, among multipletransmission schemes, for a PDSCH transmission or a PUSCH transmissionaccording to embodiments of the present disclosure;

FIG. 16 illustrates an example nested structure of PDCCH candidatesaccording to embodiments of the present disclosure;

FIG. 17 illustrates an example process for determining CCEs for PDCCHcandidates based on a first realization for a nested PDCCH search spacestructure according to embodiments of the present disclosure;

FIG. 18 illustrates an example determination of CCEs for PDCCHcandidates based on a first approach of a first realization for a nestedPDCCH search space structure according to embodiments of the presentdisclosure;

FIG. 19 illustrates an example determination of CCEs for PDCCHcandidates based on a second realization according to embodiments of thepresent disclosure;

FIG. 20 illustrates example CCE indexes of PDCCH candidates based on thesecond realization according to embodiments of the present disclosure;

FIG. 21 illustrates example control resource subsets in a controlresource set according to embodiments of the present disclosure;

FIG. 22 illustrates example CCE indexes of PDCCH candidates spanning oneor two OFDM symbols in a nested structure according to embodiments ofthe present disclosure;

FIG. 23 illustrates an example nested allocation of CCE indexes to PDCCHcandidates based on an ascending order of PDCCH candidates according toembodiments of the present disclosure;

FIG. 24 illustrates an example nested allocation of CCE indexes to PDCCHcandidates based on a restriction in CCE indexes for a number of PDCCHcandidates according to embodiments of the present disclosure;

FIG. 25 illustrates example CSI-RS transmissions in a number of NBswhere a UE retunes to an NB that the UE is configured for PDCCHreceptions after receiving a CSI-RS transmission according toembodiments of the present disclosure;

FIG. 26 illustrates example CSI-RS transmissions in a number of NBswhere a UE retunes to each NB configured for reception of a CSI-RStransmission prior to retuning to an NB configured for PDCCH receptionsaccording to embodiments of the present disclosure;

FIG. 27 illustrates example contents of a DCI format with CRC scrambledby a CSI-RS-RNTI that triggers CSI-RS transmissions in a subset of NBsfrom a set of NBs for one or more UEs according to embodiments of thepresent disclosure;

FIG. 28 illustrates example contents of a DCI format with CRC scrambledby a CSI-RS-RNTI that triggers CSI-RS transmissions in a subset of NBsfrom a set of NBs for one or more UEs and provides a PUCCH resource andTPC commands for transmissions of CSI reports according to embodimentsof the present disclosure;

FIG. 29 illustrates an example PUCCH resource determination for a UE totransmit a PUCCH conveying a CSI report based on a PUCCH resourceindicated in a DCI format triggering CSI-RS transmissions according toembodiments of the present disclosure; and

FIG. 30 illustrates a hopping pattern of an NB that a UE is configuredto receive PDCCHs according to embodiments of the present disclosure.

DETAILED DESCRIPTION

FIG. 1 through FIG. 30, discussed below, and the various embodimentsused to describe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged system or device.

The following documents are hereby incorporated by reference into thepresent disclosure as if fully set forth herein: 3GPP TS 36.211 v14.1.0,“E-UTRA, Physical channels and modulation;” 3GPP TS 36.212 v14.1.0,“E-UTRA, Multiplexing and Channel coding;” 3GPP TS 36.213 v14.1.0,“E-UTRA, Physical Layer Procedures;” 3GPP TS 36.321 v14.1.0, “E-UTRA,Medium Access Control (MAC) protocol specification;” and 3GPP TS 36.331v14.1.0, “E-UTRA, Radio Resource Control (RRC) Protocol Specification.”

FIGS. 1-4B below describe various embodiments implemented in wirelesscommunications systems and with the use of orthogonal frequency divisionmultiplexing (OFDM) or orthogonal frequency division multiple access(OFDMA) communication techniques. The descriptions of FIGS. 1-3 are notmeant to imply physical or architectural limitations to the manner inwhich different embodiments may be implemented. Different embodiments ofthe present disclosure may be implemented in any suitably-arrangedcommunications system.

FIG. 1 illustrates an example wireless network according to embodimentsof the present disclosure. The embodiment of the wireless network shownin FIG. 1 is for illustration only. Other embodiments of the wirelessnetwork 100 could be used without departing from the scope of thisdisclosure.

As shown in FIG. 1, the wireless network includes an eNB 101, an eNB102, and an eNB 103. The eNB 101 communicates with the eNB 102 and theeNB 103. The eNB 101 also communicates with at least one network 130,such as the Internet, a proprietary Internet Protocol (IP) network, orother data network.

The eNB 102 provides wireless broadband access to the network 130 for afirst plurality of user equipments (UEs) within a coverage area 120 ofthe eNB 102. The first plurality of UEs includes a UE 111, which may belocated in a small business (SB); a UE 112, which may be located in anenterprise (E); a UE 113, which may be located in a WiFi hotspot (HS); aUE 114, which may be located in a first residence (R); a UE 115, whichmay be located in a second residence (R); and a UE 116, which may be amobile device (M), such as a cell phone, a wireless laptop, a wirelessPDA, or the like. The eNB 103 provides wireless broadband access to thenetwork 130 for a second plurality of UEs within a coverage area 125 ofthe eNB 103. The second plurality of UEs includes the UE 115 and the UE116. In some embodiments, one or more of the eNBs 101-103 maycommunicate with each other and with the UEs 111-116 using 5G, LTE,LTE-A, WiMAX, WiFi, or other wireless communication techniques.

Depending on the network type, the term “base station” or “BS” can referto any component (or collection of components) configured to providewireless access to a network, such as transmit point (TP),transmit-receive point (TRP), an enhanced base station (eNodeB or eNB),a 5G base station (gNB), a macrocell, a femtocell, a WiFi access point(AP), or other wirelessly enabled devices. Base stations may providewireless access in accordance with one or more wireless communicationprotocols, e.g., 5G 3GPP new radio interface/access (NR), long termevolution (LTE), LTE advanced (LTE-A), high speed packet access (HSPA),Wi-Fi 802.11a/b/g/n/ac, etc. For the sake of convenience, the terms “BS”and “TRP” are used interchangeably in this patent document to refer tonetwork infrastructure components that provide wireless access to remoteterminals. Also, depending on the network type, the term “userequipment” or “UE” can refer to any component such as “mobile station,”“subscriber station,” “remote terminal,” “wireless terminal,” “receivepoint,” or “user device.” For the sake of convenience, the terms “userequipment” and “UE” are used in this patent document to refer to remotewireless equipment that wirelessly accesses a BS, whether the UE is amobile device (such as a mobile telephone or smartphone) or is normallyconsidered a stationary device (such as a desktop computer or vendingmachine).

Dotted lines show the approximate extents of the coverage areas 120 and125, which are shown as approximately circular for the purposes ofillustration and explanation only. It should be clearly understood thatthe coverage areas associated with eNBs, such as the coverage areas 120and 125, may have other shapes, including irregular shapes, dependingupon the configuration of the eNBs and variations in the radioenvironment associated with natural and man-made obstructions.

As described in more detail below, one or more of the UEs 111-116include circuitry, programming, or a combination thereof, for efficienttransmission structures and formats for DL control channels in anadvanced wireless communication system. In certain embodiments, and oneor more of the eNBs 101-103 includes circuitry, programming, or acombination thereof, for efficient transmission structures and formatsfor DL control channels in an advanced wireless communication system.

Although FIG. 1 illustrates one example of a wireless network, variouschanges may be made to FIG. 1. For example, the wireless network couldinclude any number of eNBs and any number of UEs in any suitablearrangement. Also, the eNB 101 could communicate directly with anynumber of UEs and provide those UEs with wireless broadband access tothe network 130. Similarly, each eNB 102-103 could communicate directlywith the network 130 and provide UEs with direct wireless broadbandaccess to the network 130. Further, the eNBs 101, 102, and/or 103 couldprovide access to other or additional external networks, such asexternal telephone networks or other types of data networks.

FIG. 2 illustrates an example eNB 102 according to embodiments of thepresent disclosure. The embodiment of the eNB 102 illustrated in FIG. 2is for illustration only, and the eNBs 101 and 103 of FIG. 1 could havethe same or similar configuration. However, eNBs come in a wide varietyof configurations, and FIG. 2 does not limit the scope of thisdisclosure to any particular implementation of an eNB.

As shown in FIG. 2, the eNB 102 includes multiple antennas 205 a-205 n,multiple RF transceivers 210 a-210 n, transmit (TX) processing circuitry215, and receive (RX) processing circuitry 220. The eNB 102 alsoincludes a controller/processor 225, a memory 230, and a backhaul ornetwork interface 235.

The RF transceivers 210 a-210 n receive, from the antennas 205 a-205 n,incoming RF signals, such as signals transmitted by UEs in the network100. The RF transceivers 210 a-210 n down-convert the incoming RFsignals to generate IF or baseband signals. The IF or baseband signalsare sent to the RX processing circuitry 220, which generates processedbaseband signals by filtering, decoding, and/or digitizing the basebandor IF signals. The RX processing circuitry 220 transmits the processedbaseband signals to the controller/processor 225 for further processing.

The TX processing circuitry 215 receives analog or digital data (such asvoice data, web data, e-mail, or interactive video game data) from thecontroller/processor 225. The TX processing circuitry 215 encodes,multiplexes, and/or digitizes the outgoing baseband data to generateprocessed baseband or IF signals. The RF transceivers 210 a-210 nreceive the outgoing processed baseband or IF signals from the TXprocessing circuitry 215 and up-converts the baseband or IF signals toRF signals that are transmitted via the antennas 205 a-205 n.

The controller/processor 225 can include one or more processors or otherprocessing devices that control the overall operation of the eNB 102.For example, the controller/processor 225 could control the reception offorward channel signals and the transmission of reverse channel signalsby the RF transceivers 210 a-210 n, the RX processing circuitry 220, andthe TX processing circuitry 215 in accordance with well-knownprinciples. The controller/processor 225 could support additionalfunctions as well, such as more advanced wireless communicationfunctions. For instance, the controller/processor 225 could support beamforming or directional routing operations in which outgoing signals frommultiple antennas 205 a-205 n are weighted differently to effectivelysteer the outgoing signals in a desired direction. Any of a wide varietyof other functions could be supported in the eNB 102 by thecontroller/processor 225.

The controller/processor 225 is also capable of executing programs andother processes resident in the memory 230, such as an OS. Thecontroller/processor 225 can move data into or out of the memory 230 asrequired by an executing process.

The controller/processor 225 is also coupled to the backhaul or networkinterface 235. The backhaul or network interface 235 allows the eNB 102to communicate with other devices or systems over a backhaul connectionor over a network. The interface 235 could support communications overany suitable wired or wireless connection(s). For example, when the eNB102 is implemented as part of a cellular communication system (such asone supporting 5G, LTE, or LTE-A), the interface 235 could allow the eNB102 to communicate with other eNBs over a wired or wireless backhaulconnection. When the eNB 102 is implemented as an access point, theinterface 235 could allow the eNB 102 to communicate over a wired orwireless local area network or over a wired or wireless connection to alarger network (such as the Internet). The interface 235 includes anysuitable structure supporting communications over a wired or wirelessconnection, such as an Ethernet or RF transceiver.

The memory 230 is coupled to the controller/processor 225. Part of thememory 230 could include a RAM, and another part of the memory 230 couldinclude a Flash memory or other ROM.

Although FIG. 2 illustrates one example of eNB 102, various changes maybe made to FIG. 2. For example, the eNB 102 could include any number ofeach component shown in FIG. 2. As a particular example, an access pointcould include a number of interfaces 235, and the controller/processor225 could support routing functions to route data between differentnetwork addresses. As another particular example, while shown asincluding a single instance of TX processing circuitry 215 and a singleinstance of RX processing circuitry 220, the eNB 102 could includemultiple instances of each (such as one per RF transceiver). Also,various components in FIG. 2 could be combined, further subdivided, oromitted and additional components could be added according to particularneeds.

FIG. 3 illustrates an example UE 116 according to embodiments of thepresent disclosure. The embodiment of the UE 116 illustrated in FIG. 3is for illustration only, and the UEs 111-115 of FIG. 1 could have thesame or similar configuration. However, UEs come in a wide variety ofconfigurations, and FIG. 3 does not limit the scope of this disclosureto any particular implementation of a UE.

As shown in FIG. 3, the UE 116 includes an antenna 305, a radiofrequency (RF) transceiver 310, TX processing circuitry 315, amicrophone 320, and receive (RX) processing circuitry 325. The UE 116also includes a speaker 330, a processor 340, an input/output (I/O)interface (IF) 345, a touchscreen 350, a display 355, and a memory 360.The memory 360 includes an operating system (OS) 361 and one or moreapplications 362.

The RF transceiver 310 receives, from the antenna 305, an incoming RFsignal transmitted by an eNB of the network 100. The RF transceiver 310down-converts the incoming RF signal to generate an intermediatefrequency (IF) or baseband signal. The IF or baseband signal is sent tothe RX processing circuitry 325, which generates a processed basebandsignal by filtering, decoding, and/or digitizing the baseband or IFsignal. The RX processing circuitry 325 transmits the processed basebandsignal to the speaker 330 (such as for voice data) or to the processor340 for further processing (such as for web browsing data).

The TX processing circuitry 315 receives analog or digital voice datafrom the microphone 320 or other outgoing baseband data (such as webdata, e-mail, or interactive video game data) from the processor 340.The TX processing circuitry 315 encodes, multiplexes, and/or digitizesthe outgoing baseband data to generate a processed baseband or IFsignal. The RF transceiver 310 receives the outgoing processed basebandor IF signal from the TX processing circuitry 315 and up-converts thebaseband or IF signal to an RF signal that is transmitted via theantenna 305.

The processor 340 can include one or more processors or other processingdevices and execute the OS 361 stored in the memory 360 in order tocontrol the overall operation of the UE 116. For example, the processor340 could control the reception of forward channel signals and thetransmission of reverse channel signals by the RF transceiver 310, theRX processing circuitry 325, and the TX processing circuitry 315 inaccordance with well-known principles. In some embodiments, theprocessor 340 includes at least one microprocessor or microcontroller.

The processor 340 is also capable of executing other processes andprograms resident in the memory 360, such as processes for beammanagement. The processor 340 can move data into or out of the memory360 as required by an executing process. In some embodiments, theprocessor 340 is configured to execute the applications 362 based on theOS 361 or in response to signals received from eNBs or an operator. Theprocessor 340 is also coupled to the I/O interface 345, which providesthe UE 116 with the ability to connect to other devices, such as laptopcomputers and handheld computers. The I/O interface 345 is thecommunication path between these accessories and the processor 340.

The processor 340 is also coupled to the touchscreen 350 and the display355. The operator of the UE 116 can use the touchscreen 350 to enterdata into the UE 116. The display 355 may be a liquid crystal display,light emitting diode display, or other display capable of rendering textand/or at least limited graphics, such as from web sites.

The memory 360 is coupled to the processor 340. Part of the memory 360could include a random access memory (RAM), and another part of thememory 360 could include a Flash memory or other read-only memory (ROM).

Although FIG. 3 illustrates one example of UE 116, various changes maybe made to FIG. 3. For example, various components in FIG. 3 could becombined, further subdivided, or omitted and additional components couldbe added according to particular needs. As a particular example, theprocessor 340 could be divided into multiple processors, such as one ormore central processing units (CPUs) and one or more graphics processingunits (GPUs). Also, while FIG. 3 illustrates the UE 116 configured as amobile telephone or smartphone, UEs could be configured to operate asother types of mobile or stationary devices.

The present disclosure relates generally to wireless communicationsystems and, more specifically, to improving a PDCCH receptionreliability and reducing an associated signaling overhead. Acommunication system includes a downlink (DL) that refers totransmissions from a base station or one or more transmission points toUEs and an uplink (UL) that refers to transmissions from UEs to a basestation or to one or more reception points.

To meet the demand for wireless data traffic having increased sincedeployment of 4G communication systems, efforts have been made todevelop an improved 5G or pre-5G communication system. Therefore, the 5Gor pre-5G communication system is also called a “beyond 4G network” or a“post LTE system.” The 5G communication system is considered to beimplemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, soas to accomplish higher data rates. To decrease propagation loss of theradio waves and increase the transmission distance, the beamforming,massive multiple-input multiple-output (MIMO), full dimensional MIMO(FD-MIMO), array antenna, an analog beam forming, large scale antennatechniques are discussed in 5G communication systems. In addition, in 5Gcommunication systems, development for system network improvement isunder way based on advanced small cells, cloud radio access networks(RANs), ultra-dense networks, device-to-device (D2D) communication,wireless backhaul, moving network, cooperative communication,coordinated multi-points (CoMP), reception-end interference cancellationand the like. In the 5G system, Hybrid FSK and QAM modulation (FQAM) andsliding window superposition coding (SWSC) as an advanced codingmodulation (ACM), and filter bank multi carrier (FBMC), non-orthogonalmultiple access (NOMA), and sparse code multiple access (SCMA) as anadvanced access technology have been developed.

A time unit for DL signaling or for UL signaling on a cell is referredto as a slot and can include one or more slot symbols. A slot symbol canalso serve as an additional time unit. A frequency (or bandwidth (BW))unit is referred to as a resource block (RB). One RB includes a numberof sub-carriers (SCs). For example, a slot can have duration of 0.5milliseconds or 1 millisecond, include 7 symbols or 14 symbols,respectively, and an RB can have a BW of 180 KHz and include 12 SCs withinter-SC spacing of 15 KHz or 60 KHz.

DL signals include data signals conveying information content, controlsignals conveying DL control information (DCI), and reference signals(RS) that are also known as pilot signals. A gNB can transmit datainformation or DCI through respective physical DL shared channels(PDSCHs) or physical DL control channels (PDCCHs). A gNB can transmitone or more of multiple types of RS including channel state informationRS (CSI-RS) and demodulation RS (DMRS). A CSI-RS is intended for UEs tomeasure channel state information (CSI). A DMRS is transmitted only inthe BW of a respective PDCCH or PDSCH and a UE can use the DMRS todemodulate data or control information.

FIG. 4 illustrates an example DL slot structure 400 for PDSCHtransmission or PDCCH transmission according to embodiments of thepresent disclosure. An embodiment of the DL slot structure 400 shown inFIG. 4 is for illustration only. One or more of the componentsillustrated in FIG. 4 can be implemented in specialized circuitryconfigured to perform the noted functions or one or more of thecomponents can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

As shown in FIG. 4, a slot 410 includes N_(symb) ^(DL)=7 symbols 420where a gNB transmits data information, DCI, or DMRS. A DL system BWincludes N RBs. Each RB includes N_(sc) ^(RB) SCs. For example N_(sc)^(RB)=12. A UE is assigned M_(PDSCH) RBs for a total of M_(sc)^(PDSCH)=M_(PDSCH)·N_(sc) ^(RB) SCs 430 for a PDSCH transmission BW. APDCCH conveying DCI is transmitted over control channel elements (CCEs)that are substantially spread across the DL system BW. For example, afirst slot symbol 440 can be used by the gNB to transmit DCI and DMRS. Asecond slot symbol 450 can be used by the gNB to transmit DCI or data orDMRS. Remaining slot symbols 460 can be used by the gNB to transmitPDSCH, DMRS associated with each PDSCH, and CSI-RS. In some slots, thegNB can also transmit synchronization signals and system information.

UL signals also include data signals conveying information content,control signals conveying UL control information (UCI), and RS. A UEtransmits data information or UCI through a respective physical ULshared channel (PUSCH) or a physical UL control channel (PUCCH). When aUE simultaneously transmits data information and UCI, the UE canmultiplex both in a PUSCH or transmit them separately in respectivePUSCH and PUCCH. UCI includes hybrid automatic repeat requestacknowledgement (HARQ-ACK) information, indicating correct or incorrectdetection of data transport blocks (TB s) by a UE, scheduling request(SR) indicating whether a UE has data in the UE's buffer, and CSIreports enabling a gNB to select appropriate parameters for PDSCH orPDCCH transmissions to a UE.

A CSI report from a UE can include a channel quality indicator (CQI)informing a gNB of a maximum modulation and coding scheme (MCS) for theUE to detect a data TB with a predetermined block error rate (BLER),such as a 10% BLER, of a precoding matrix indicator (PMI) informing agNB how to precode signaling to a UE, and of a rank indicator (RI)indicating a transmission rank for a PDSCH. UL RS includes DMRS andsounding RS (SRS). DMRS is transmitted only in a BW of a respectivePUSCH or PUCCH transmission. A gNB can use a DMRS to demodulateinformation in a respective PUSCH or PUCCH. SRS is transmitted by a UEto provide a gNB with an UL CSI and, for a TDD or a flexible duplexsystem, to also provide a PMI for DL transmissions. An UL DMRS or SRStransmission can be based on a transmission of a Zadoff-Chu (ZC)sequence or, in general, of a CAZAC sequence.

FIG. 5 illustrates an example UL slot structure 500 for PUSCHtransmission or PUCCH transmission according to embodiments of thepresent disclosure. An embodiment of the UL slot structure 500 shown inFIG. 5 is for illustration only. One or more of the componentsillustrated in FIG. 5 can be implemented in specialized circuitryconfigured to perform the noted functions or one or more of thecomponents can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

As shown in FIG. 5, a slot 510 includes N_(symb) ^(UL)=7 symbols 520where UE transmits data information, UCI, or RS including one symbolwhere the UE transmits DMRS 530. An UL system BW includes N_(RB) ^(UL)RBs. Each RB includes N_(sc) ^(RB) SCs. A UE is assigned M_(PUXCH) RBsfor a total of M_(sc) ^(PUXCH)=M_(PUXCH)·N_(sc) ^(RB) SCs 540 for aPUSCH transmission BW (“X”=“S”) or for a PUCCH transmission BW(“X”=“C”). A last one or more slot symbols can be used to multiplexPUCCH transmissions or SRS transmissions from one or more UEs.

A hybrid slot includes symbols for DL transmissions, one or more symbolsfor a guard period (GP), and symbols for UL transmissions, similar to aspecial SF. For example, symbols for DL transmissions can convey PDCCHand PDSCH transmissions and symbols for UL transmissions can conveyPUCCH transmissions. For example, symbols for DL transmissions canconvey PDCCH transmissions and symbols for an UL transmission can conveyPUSCH and PUCCH transmissions.

FIG. 6 illustrates an example hybrid slot structure 600 for DLtransmissions and UL transmissions according to embodiments of thepresent disclosure. An embodiment of the hybrid slot structure 600 shownin FIG. 6 is for illustration only. One or more of the componentsillustrated in FIG. 6 can be implemented in specialized circuitryconfigured to perform the noted functions or one or more of thecomponents can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

As shown in FIG. 6, a slot 610 consists of a number of symbols 620 thatinclude a symbol for DCI transmissions and DMRS in respective PDCCHs630, four symbols for data transmissions in respective PDSCHs 640, a GPsymbol 650 to provide a guard time for the UE to switch from DLreception to UL transmission, and an UL symbol for transmitting UCI on aPUCCH 660. In general, any partitioning between DL symbols and ULsymbols of a hybrid slot is possible by sliding the location of the GPsymbol from the second symbol of a slot to the second to last symbol ofa slot. The GP can also be shorter than one slot symbol and theadditional time duration can be used for DL transmissions or for ULtransmissions with shorter symbol duration. GP symbols do not need to beexplicitly included in a slot structure and can be provided in practicefrom the gNB scheduler by not scheduling transmissions to UEs ortransmissions from UEs in such symbols.

DL transmissions and UL transmissions can be based on an orthogonalfrequency division multiplexing (OFDM) waveform including a variantusing DFT preceding that is known as DFT-spread-OFDM.

FIG. 7 illustrates an example transmitter structure 700 using OFDMaccording to embodiments of the present disclosure. An embodiment of thetransmitter structure 700 shown in FIG. 7 is for illustration only. Oneor more of the components illustrated in FIG. 7 can be implemented inspecialized circuitry configured to perform the noted functions or oneor more of the components can be implemented by one or more processorsexecuting instructions to perform the noted functions. Other embodimentsare used without departing from the scope of the present disclosure.

As shown in FIG. 7, information bits, such as DCI bits or data bits 710,are encoded by encoder 720, rate matched to assigned time/frequencyresources by rate matcher 730, and modulated by modulator 740.Subsequently, modulated encoded symbols and DMRS or CSI-RS 750 aremapped to SCs 760 by SC mapping unit 765, an inverse fast Fouriertransform (IFFT) is performed by filter 770, a cyclic prefix (CP) isadded by CP insertion unit 780, and a resulting signal is filtered byfilter 790 and transmitted by an radio frequency (RF) unit 795.

FIG. 8 illustrates an example receiver structure 800 using OFDMaccording to embodiments of the present disclosure. An embodiment of thereceiver structure 800 shown in FIG. 8 is for illustration only. One ormore of the components illustrated in FIG. 8 can be implemented inspecialized circuitry configured to perform the noted functions or oneor more of the components can be implemented by one or more processorsexecuting instructions to perform the noted functions. Other embodimentsare used without departing from the scope of the present disclosure.

As shown in FIG. 8, a received signal 810 is filtered by filter 820, aCP removal unit removes a CP 830, a filter 840 applies a fast Fouriertransform (FFT), SCs de-mapping unit 850 de-maps SCs selected by BWselector unit 855, received symbols are demodulated by a channelestimator and a demodulator unit 860, a rate de-matcher 870 restores arate matching, and a decoder 880 decodes the resulting bits to provideinformation bits 890.

A UE typically monitors multiple candidate locations for respectivepotential PDCCH transmissions to decode multiple DCI formats in a slot.A DCI format includes cyclic redundancy check (CRC) bits in order forthe UE to confirm a correct detection of the DCI format. A DCI formattype is identified by a radio network temporary identifier (RNTI) thatscrambles the CRC bits. For a DCI format scheduling a PDSCH or a PUSCHto a single UE, the RNTI can be a cell RNTI (C-RNTI) and serves as a UEidentifier.

For a DCI format scheduling a PDSCH conveying system information (SI),the RNTI can be an SI-RNTI. For a DCI format scheduling a PDSCHproviding a random access response (RAR), the RNTI can be an RA-RNTI.For a DCI format providing TPC commands to a group of UEs, the RNTI canbe a TPC-PUSCH-RNTI or a TPC-PUCCH-RNTI. Each RNTI type can beconfigured to a UE through higher-layer signaling such as RRC signaling.A DCI format scheduling PDSCH transmission to a UE is also referred toas DL DCI format or DL assignment while a DCI format scheduling PUSCHtransmission from a UE is also referred to as UL DCI format or UL grant.

FIG. 9 illustrates an example encoding process 900 for a DCI formataccording to embodiments of the present disclosure. An embodiment of theencoding process 900 shown in FIG. 9 is for illustration only. One ormore of the components illustrated in FIG. 9 can be implemented inspecialized circuitry configured to perform the noted functions or oneor more of the components can be implemented by one or more processorsexecuting instructions to perform the noted functions. Other embodimentsare used without departing from the scope of the present disclosure.

As shown in FIG. 9, a gNB separately encodes and transmits each DCIformat in a respective PDCCH. When applicable, an RNTI for a UE that aDCI format is intended for masks a CRC of the DCI format codeword inorder to enable the UE to identify the DCI format. For example, the CRCand the RNTI can include 16 bits. Otherwise, when an RNTI is notincluded in a DCI format, a DCI format type indicator field can beincluded in the DCI format. The CRC of (non-coded) DCI format bits 910is determined using a CRC computation unit 920, and the CRC is maskedusing an exclusive OR (XOR) operation unit 930 between CRC bits and RNTIbits 940. The XOR operation is defined as XOR(0,0)=0, XOR(0,1)=1,XOR(1,0)=1, XOR(1,1)=0. The masked CRC bits are appended to DCI formatinformation bits using a CRC append unit 950. An encoder 960 performschannel coding (such as tail-biting convolutional coding or polarcoding), followed by rate matching to allocated resources by ratematcher 970. Interleaving and modulation units 980 apply interleavingand modulation, such as QPSK, and the output control signal 990 istransmitted.

FIG. 10 illustrates an example decoding process 1000 for a DCI formatfor use with a UE according to embodiments of the present disclosure. Anembodiment of the decoding process 1000 shown in FIG. 10 is forillustration only. One or more of the components illustrated in FIG. 10can be implemented in specialized circuitry configured to perform thenoted functions or one or more of the components can be implemented byone or more processors executing instructions to perform the notedfunctions. Other embodiments are used without departing from the scopeof the present disclosure.

As shown in FIG. 10, a received control signal 1010 is demodulated andde-interleaved by a demodulator and a de-interleaver 1020. A ratematching applied at a gNB transmitter is restored by rate matcher 1030,and resulting bits are decoded by decoder 1040. After decoding, a CRCextractor 1050 extracts CRC bits and provides DCI format informationbits 1060. The DCI format information bits are de-masked 1070 by an XORoperation with an RNTI 1080 (when applicable) and a CRC check isperformed by unit 1090. When the CRC check succeeds (check-sum is zero),the DCI format information bits are considered to be valid. When the CRCcheck does not succeed, the DCI format information bits are consideredto be invalid.

A PDCCH transmission is in RBs and symbols of a control resource set. AUE can be configured RBs and symbols for one or multiple controlresource sets. A PDCCH is transmitted using an aggregation of one orseveral control channel elements (CCEs). A block of encoded andmodulated symbols of a DCI format are mapped in sequence to resourceelements (k,l), across SC index k and slot symbol l, on an associatedantenna port that are part of the CCEs assigned for the PDCCHtransmission. A PDCCH transmission can be distributed in frequency, andis then also referred to as interleaved PDCCH transmission, or localizedin frequency and is then also referred to as non-interleaved PDCCHtransmission.

For example, l∈{0, 1}. A PDCCH search space can be common to UEs or canbe UE-specific when a UE is configured a C-RNTI equal to n_(RNTI). Forexample, for the common search space Y_(k) is set to 0 for two CCEaggregation levels L=4 and L=8, while for the UE-specific search spaceS_(k) ^((L)) at CCE aggregation level L, the variable Y_(k) is definedby Y_(k)=(A·Y_(k-1))mod D where Y⁻¹=n_(RNTI)≠0, A=39827, D=65537 and kis a slot number. For example, for an aggregation level of L CCEs, thelocation of CCEs for PDCCH candidate m in a subframe k that includesN_(CCE,k) CCEs can be determined as L{(Y_(k)+m′)mod └N_(CCE,k)/L┘}+i,i=0, . . . L−1. When a UE is not configured with a C-RNTI, a searchspace is common to all UEs.

An important objective in the design of PDCCH transmissions is toimprove a respective reliability. This can be achieved through severalmechanisms including support of frequency diversity or beam-forming,enabling accurate channel estimation, improved coverage, andminimization of DCI format sizes. Improved reliability for PDCCHtransmissions can offer improved throughput, as decoding of a PDCCHconveying a DCI format scheduling data transmission to one or UEs ordata transmission from one or more UEs is less likely to be incorrect,and reduced overhead for PDCCH transmissions as fewer resources need tobe used thereby allowing more resources to be used for datatransmissions. Further, a DCI format may enable dynamic switching of atransmission mode while minimizing an associated payload.

PDCCH transmissions need to also be able to schedule PDSCH transmissionswith reduced latency and improved reception reliability. This typicallyimplies that PDCCH and PDSCH transmissions are over a small number ofsymbols, PDSCH transmissions convey small transport block sizes, andPDCCH can represent a material overhead. In such cases, it is importantto minimize an overhead associated with PDCCH transmission by enablingre-use for PDSCH demodulation of a DMRS used for PDCCH demodulation.

UEs communicating with a gNB need to be able to perform time trackingand frequency tracking in order to be able to maintain reliablecommunication with the gNB. Typically, this is achieved by the gNBtransmitting an RS that UEs can use for time tracking and frequencytracking. To minimize an overhead associated with a transmission of suchRS, it is desirable that the RS is not continuously transmitted, evenperiodically, and that the RS can be an RS also used for otherfunctionalities such as a DMRS used for PDCCH demodulation.

Therefore, there is a need to design a PDCCH transmission enablingfrequency diversity with enhanced channel estimation. There is a need todesign a PDCCH transmission enabling beam-forming and enhanced channelestimation. There is a need to enable DMRS re-use for demodulation ofPDCCH transmissions and of PDSCH transmissions. There is another need toenable configurable CCE aggregation levels for PDCCH transmissions in acommon search space. Finally, there is another need to enable DMRSre-use for time tracking and frequency tracking and for demodulation ofPDCCH transmissions.

In some embodiments, a CCE structure for distributed PDCCH transmissionsthat depends on a respective aggregation level is considered in order toenable frequency diversity and enhanced channel estimation. Use of asmall CCE aggregation level is typically associated with UEsexperiencing a relatively high SINR while use of a large CCE aggregationlevel is typically associated with UEs experiencing a relatively lowSINR. Channel estimation accuracy has a strong dependence on the SINRand the lower the SINR, the worse the channel estimation accuracy, andthe larger the degradation in PDCCH reception reliability due toinaccurate channel estimation. Conversely, frequency diversity is aproperty of a PDCCH transmission structure and does not depend on theSINR. Therefore, a design objective is to enable sufficient frequencydiversity while also enabling an accuracy of a channel estimate toincrease as a CCE aggregation level for an associated PDCCH transmissionincreases. Typically, a frequency diversity of an order of about two orfour is sufficient to capture nearly all frequency diversity gainsoffered by a channel medium.

The following descriptions assume that one CCE includes four ins but anyother number of RBs, such as six RBs, can also apply. For a frequencydistributed PDCCH transmission that includes one CCE or four RBs,respective RBs can be distributed in frequency and are not adjacent infrequency. This enables the PDCCH transmission to capture nearly allfrequency diversity gains that a channel medium can provide but a DMRSused for that estimation needs to be confined within each RB and it isnot generally beneficial for a UE to filter channel estimates obtainedacross frequency distributed RBs. An RB is equivalent to a resourceelement group (REG).

For a frequency distributed PDCCH transmission that eludes two CCEs oreight channel estimation can improve by distributing four pairs RBs infrequency. Then, for demodulating a PDCCH candidate that includes twoCCEs, a UE can filter a DMRS in pairs of RBs, assuming a sane DMRSprecoding in each pair of RBs, to improve a respective reliability of achannel estimate. Similar, for a frequency distributed PDCCHtransmission that includes four CCEs or eight CCEs, corresponding to oren or thirty two RBs respectively, transmission can be in blocks of fourRBs or in blocks of eight RBs that are distributed in frequency (overfour respective frequency locations assuming a transmission bandwidthlarger than thirty two RBs).

Then, a UE can filter a DMRS within respective blocks of RBs and improvea respective reliability of a channel estimate while an associated PDCCHtransmission can obtain all frequency diversity gains from the channelmedium. It is also possible for a frequency distributed PDCCHtransmission to be in blocks of RBs starting from an aggregation levelof one CCE. For example, when a CCE includes six RBs, a PDCCHtransmission with an aggregation level of one CCE to a UE can be inblocks of two RBs over three frequency non-contiguous blocks of two RBsin a DL system bandwidth configured for PDCCH transmissions to the UE.

In general, for a CCE that includes N_(CCE) ^(RBs), a UE can beconfigured by higher layers a number of N_(bundle) RBs forming a blockof frequency-contiguous RBs and a distributed CCE-to-RB mapping can bein blocks of N_(bundle) RBs for a total of N_(CCE) ^(RBs)/N_(bundle)frequency distributed blocks of N_(bundle) RBs. For example, for acontrol resource set that includes one symbol, N_(CCE) ^(RBs)=6, andN_(bundle)=2, there are N_(CCE) ^(RBs)/N_(bundle)=3 frequencydistributed blocks while for N_(CCE) ^(RBs)=6 and N_(bundle)=6, N_(CCE)^(RBs)/N_(bundle)=1 there is only one block of N_(bundle)=6 frequencycontiguous RBs. For a given DMRS antenna port is an RB, a UE can assumethat a same precoder applies to all RBs in a bundle of RBs. It is alsopossible for the bundle of RBs to be larger than N_(CCE) ^(RBs).

This can be useful for transmissions of UE-common PDCCHs, for example ina common search space (CSS), where a DMRS can be UE-common. For example,for a PDCCH transmission in a control resource set spanning a BW ofN_(total) RBs, a UE can be configured to assume a same DMRS precodingover a number of RBs that can be equal to N_(total) or N_(total)/2 orN_(total)/4. This can allow a UE to filter a DMRS over a larger numberof RBs and improve a channel estimate.

For the CSS, N_(bundle) can be predefined in a system operation or besignaled by broadcast system information such as a master informationblock (MIB) or a secondary system information block (SIB). For example,a PDCCH scheduling a transmission of a first SIB can have a bundle sizethat is predetermined in the system operation while a PDCCH scheduling atransmission of a second SIB or of a RAR can have a bundle size that issignaled in the first SIB.

A CCE can be transmitted over one OFDM symbol. Coverage enhancements canbe obtained, when necessary, by using larger CCE aggregation levels fora PDCCH transmission and distributed respective CCEs over multiple OFDMsymbols. For example, for a DL control resource set that includesN_(control) ^(set) OFDM symbols in a slot and a PDCCH candidatecorresponding to an aggregation level of L CCEs, CCE i, i=0, . . . L−1,can be located in OFDM symbol with index determined as i mod(N_(control)^(set)−1) in case of frequency-first REG-to-CCE mapping.

For a DL control resource set that includes M_(control) ^(set) RBs, thefirst block of RBs can start at RB with index (m+O)mod(M_(control)^(set)−1), the second block of RBs can start at RB with index (m+O+└mod(M_(control) ^(set)−1)/4┘)mod(M_(control) ^(set)−1), the third blockof RBs can start at RB with index (m+O+2·└ mod(M_(control)^(set)−1)/4┘)mod(M_(control) ^(set)−1), and the fourth block of RBs canstart at RB with index (m+O+3·└ mod(M_(control)^(set)−1)/4┘)mod(M_(control) ^(set)−1), where 0 is a UE-specific offsetor a cell-specific offset that can be, for example, determined from aC-RNTI for the UE, or explicitly configured using higher layer signalingby a gNB, or determined by an identity of a cell where the PDCCH istransmitted.

FIG. 11 illustrates an example distributed PDCCH transmission structure1100 depending on a respective CCE aggregation level according toembodiments of the present disclosure. An embodiment of the distributedPDCCH transmission structure 1100 shown in FIG. 11 is for illustrationonly. One or more of the components illustrated in FIG. 11 can beimplemented in specialized circuitry configured to perform the notedfunctions or one or more of the components can be implemented by one ormore processors executing instructions to perform the noted functions.Other embodiments are used without departing from the scope of thepresent disclosure.

For a PDCCH transmission with aggregation level of one CCE that includesfour RBs, the RBs are distributed in frequency per single RB 1110. For aPDCCH transmission with aggregation level of two CCEs and time-firstmapping of CCEs, the respective eight RBs are distributed in frequencyin blocks of two adjacent RBs where the first RB from a block of RBs inon a first OFDM symbol for the first CCE and the second RB from theblock of RBs in on a second OFDM symbol for the second CCE 1120.

For a PDCCH transmission with aggregation level of two CCEs andfrequency-first mapping of CCEs, the respective eight RBs aredistributed in frequency in blocks of two adjacent RBs where each ablock of RBs is on a same OFDM symbol 1130. Similar structures can applyfor PDCCH transmissions with CCE aggregation levels larger than twoCCEs. For time first mapping, when there are fewer OFDM symbols thanCCEs for a CCE aggregation level, such as for example when there are twoOFDM symbols for mapping an aggregation level of four CCEs, wrap aroundcan apply for the mapping of CCEs 1140.

The mapping of CCEs to RBs in FIG. 11 considers interleaving of RBs perOFDM symbol to obtain distributed (non-consecutive) indexes of RBs inthe physical domain from contiguous (consecutive) RB indexes in thelogical domain that form a CCE. Otherwise, if interleaving was not perOFDM symbol but instead was over both OFDM symbols, it would not bepossible to have RBs for a given CCE located in only one OFDM symbol.

A different mapping of CCEs to OFDM symbols can be configured fordifferent PDCCH transmission types. For example, time-first mapping canapply for a beam-formed localized PDCCH transmission to a UE in order tomaximize a localization of the beam-formed PDCCH transmission andmaximize associated precoding gains while frequency-first mapping canapply for a frequency distributed PDCCH transmission using transmitterantenna diversity in order to maximize frequency diversity gains.

For a PDCCH transmission with aggregation level of one CCE that includesfour RBs and time-first CCE-to-REG mapping, the RBs of an REG bundle arefirst distributed in time per OFDM symbol. When a DL control resourceset has N_(control) ^(set) OFDM symbols that are fewer than a number ofRBs N_(RB) ^(L) for an aggregation level of L CCEs, a wrap-around isapplied in the time domain for the N_(bundle) RBs and a N_(control)^(set)+1 RB is contiguous to a first RB in a first OFDM symbol, aN_(control) ^(set)+2 RB is contiguous to a first RB in a second OFDMsymbol, a 2·N_(control) ^(set)+1 RB is contiguous to a second RB in afirst OFDM symbol, a 2·N_(control) ^(set)+2 RB is contiguous to a firstRB in a second OFDM symbol, and so on. In general, a p·N_(control)^(set)+q RB is contiguous to the p−1 RB in the q OFDM symbol.

FIG. 12 illustrates an example localized PDCCH transmission structure1200 depending on a respective CCE aggregation level according toembodiments of the present disclosure. An embodiment of the localizedPDCCH transmission structure 1200 shown in FIG. 12 is for illustrationonly. One or more of the components illustrated in FIG. 12 can beimplemented in specialized circuitry configured to perform the notedfunctions or one or more of the components can be implemented by one ormore processors executing instructions to perform the noted functions.Other embodiments are used without departing from the scope of thepresent disclosure.

As shown in FIG. 12, for a DL control resource set includes N_(control)^(set)=2 symbols 1210 and a PDCCH transmission with an aggregation levelof one CCE that includes four RBs, a first and a third RB are mappedconsecutively in frequency on a first OFDM symbol and a second and afourth RB are mapped consecutively in frequency on a second OFDM symbolfor each PDCCH candidate. For a DL control resource set includesNN_(control) ^(set)=4 symbols 1220 and a PDCCH transmission with anaggregation level of one CCE that includes four RBs, a first, second,third, and fourth RB is mapped respectively on a same RB index on afirst, second, third, and fourth OFDM symbol. PDCCH candidates aredistributed in frequency.

A CCE mapping as in FIG. 11 or as in FIG. 12 can allow coexistence in asame bandwidth of UEs with different bandwidth reception capabilitiesand coexistence of a common search space and of a UE-specific searchspace in a same DL control resource set.

A UE can be configured to monitor different DL control resource sets,associated with different search spaces, in different symbols of a slotor in different slots. The configuration can be by UE-group commonhigher layer signaling or by UE-specific higher layer signaling. Forexample, a UE can be configured to monitor a first DL control resourceset associated with a common search space in a first one or more symbolsof a slot and be configured to monitor a second DL control resource setassociated with a UE-specific search space in second one or more symbolsof a slot, for example immediately after the first one or more symbolsof a slot.

For example, a UE can be configured to monitor a first DL controlresource set associated with a first common search space in a first oneor more symbols of a slot and be separately configured to monitor asecond DL control resource set associated with a second common searchspace in second one or more symbols of a slot, for example immediatelyafter the first one or more symbols of a slot. For example, a UE can beconfigured to monitor a first DL control resource set associated with afirst UE-specific search space, for example for transmissions from afirst beam, in a first one or more symbols of a slot and be configuredto monitor a second DL control resource set associated with a secondUE-specific search space for transmissions from a second beam in secondone or more symbols of a slot, for example immediately after the firstone or more symbols of a slot.

For example, a UE can be configured to monitor a first DL controlresource set according to parameters, such as PDCCH candidates ortransmission scheme, such as distributed or localized PDCCHtransmission, associated with a common search space in a first number ofslots in a period of slots and monitor the first DL control resource setaccording to parameters associated with a UE-specific search space in asecond number of slots in the period of slots. The period of slots canbe determined in a system operation, such as 10 slots or 20 slots, or beconfigured to a UE by UE-group common or UE-specific higher layersignaling. Monitoring of a search space by a UE means that the UEperforms decoding operations for PDCCH candidates using respective CCEsin the search space.

A UE can monitor UE-specific DCI formats both in a common search spaceand in a UE-specific search space. To enable this functionality, a UEcan adjust parameters for a reception of a UE-specific DCI format in acontrol resource set according to an associated search space type(common or UE-specific). For example, a sequence scrambling atransmission of a DMRS associated with a UE-specific DCI formattransmission in a PDCCH can be a first scrambling sequence when thetransmission is in a common search space, and a second scramblingsequence when the transmission is in a UE-specific search space. Forexample, a number of sub-carriers used for DMRS transmission in an RBcan have a first value in a common search space and a second value in aUE-specific search space. For example, a first transmission scheme, suchas transmit antenna diversity for distributed PDCCH transmission, can beassociated with DCI format reception in a common search space and asecond transmission scheme, such as precoding/beamforming for alocalized PDCCH transmission, can be associated with DCI formatreception in a UE-specific search space.

A UE can also be configured to monitor a first search space with a firstperiodicity and a second search space with a second periodicity. Forexample, the first search space can be a common search space and aperiodicity can be five slots and the second search space can be aUE-specific search space and the periodicity can be one slot. Forexample, the first search space can be a first UE-specific search spaceand a periodicity can be one slot and the second search space can be asecond UE-specific search space and the periodicity can be one-fifth orone-half of a slot. A number of decoding operations that a UE canperform during a time period can therefore depend on a number of searchspaces the UE monitors during that period.

For example, in time periods when the UE does not monitor a commonsearch space, associated PDCCH decoding operations can be used formonitoring a UE-specific search space. A number of PDCCH candidates, atleast for some CCE aggregation levels for a UE-specific search space,can be larger in time periods where the UE does not monitor a commonsearch space. For example, in time period when a UE does not monitor aUE-specific search space associated with a longer periodicity,corresponding PDCCH decoding operations can be allocated to monitoring aUE-specific search space associated with a shorter periodicity. A numberof PDCCH candidates at least for some CCE aggregation levels for aUE-specific search space with a shorter monitoring periodicity can belarger in time periods where the UE does not monitor a UE-specificsearch space with a longer monitoring periodicity.

For each serving cell, higher layer signaling configures a UE with Pcontrol resource sets. For control resource set p, 0≤p<P, theconfiguration can include: a subcarrier spacing and a CP length; a firstsymbol index provided by higher layer parameter CORESET-start-symb; anumber of consecutive symbols provided by higher layer parameter[CORESET-time-duration]; a set of resource blocks provided by higherlayer parameter CORESET-freq-dom; CCE-to-REG mapping provided by higherlayer parameter CORESET-trans-type; and/or an REG bundle size, in caseof interleaved CCE-to-REG mapping, provided by higher layer parameterCORESET-REG-bundle-size; whether the PDCCH transmission is distributedor localized provided by a higher layer parameterCORESET-CCE-REG-mapping-type, or an antenna port quasi-collocationprovided by higher layer parameter [CORESET-QCL-Configld].

For each serving cell and for each DCI format that a UE is configured tomonitor PDCCH, the UE is configured the following associations tocontrol resource sets: a set of control resource sets by higher layerparameter DCI-to-CORESET-map; a number of PDCCH candidates per CCEaggregation level L per control resource set in the set of controlresource sets by higher layer parameter CORESET-candidates-DCI; and/or amonitoring periodicity of k_(p) symbols per control resource set in theset of control resource sets, in non-DRX mode operation, by higher layerparameter CORESET-monitor-period-DCI.

Each control resource set includes a set of CCEs numbered from 0 toN_(CCE,p,k) _(p) −1 where N_(CCE,p,k) _(p) is the number of CCEs incontrol resource set p in monitoring period k_(p). The monitoringperiods can be indexed within (modulo) a predetermined time period, suchas a number of system frame numbers, a system frame number cycle, or apredetermined duration such as 40 milliseconds.

The sets of PDCCH candidates that a UE monitors are defined in terms ofPDCCH UE-specific search spaces. A PDCCH UE-specific search space S_(k)_(p) ^((L)) at CCE aggregation level L, such as L∈{1, 2, 4, 8, 16}, isdefined by a set of PDCCH candidates for CCE aggregation level L.

If a UE is configured with higher layer parameter cif-InSchedulingCellthe carrier indicator field value corresponds to cif-InSchedulingCell.

For a serving cell on which a UE monitors PDCCH candidates in aUE-specific search space, if the UE is not configured with a carrierindicator field, the UE monitors the PDCCH candidates without carrierindicator field. For a serving cell on which a UE monitors PDCCHcandidates in a UE-specific search space, if a UE is configured with acarrier indicator field, the UE monitors the PDCCH candidates withcarrier indicator field.

For a control resource set p and for a DCI format A, for example for P=2control resource sets, the CCEs corresponding to PDCCH candidate m_(n)_(CI) of the search space for a serving cell corresponding to carrierindicator field value n_(CI) are given by:

$\begin{matrix}{{L \cdot \{ {( {Y_{p,k} + \lfloor \frac{m_{n_{CI}} \cdot N_{{CCE},p,k_{p}}}{L \cdot M_{p,{{ma}\; x}}^{(L)}} \rfloor + n_{CI}} ){mod}\lfloor {N_{{CCE},p,k_{p}}/L} \rfloor} \}} + i} & {{equation}\mspace{14mu} 1}\end{matrix}$

where Y_(p,k)=(A_(p)·Y_(p,k) _(p) ⁻¹)mod D, Y_(p,−1)=n_(RNTI)≠0,A₀=39827, A₁=39829, and D=65537; i=0, . . . , L−1; n_(CI) is the carrierindicator field value if the UE is configured with a carrier indicatorfield for the serving cell on which PDCCH is monitored; otherwisen_(CI)=0; M_(p,max) ^((L)) is the maximum number of PDCCH candidatesthat can be either among all configured DCI formats or only for the DCIformat A, over all configured n_(CI) values for a CCE aggregation levelL in control) resource set p; m_(n) _(CI) =0, . . . M_(p,n) _(CI)^((L))−1, where M_(p,n) _(CI) ^((L)) is the number of PDCCH candidatesthe UE is configured to monitor for aggregation level L for a servingcell corresponding to n_(CI); n_(RNTI) is the RNTI value used for therespective DCI format.

As M_(p,max) ^((L)) can be different at different PDCCH monitoringperiods k_(p), the value of M_(p,max) ^((L)) can depend on the PDCCHmonitoring period and therefore, M_(p,max) ^((L)) can be replaced byM_(p,k) _(p) _(,max) ^((L)). Therefore, M_(p,max) ^((L)) can be themaximum number of PDCCH candidates, either among all configured DCIformats or only for the DCI format A, over all configured n_(CI) valuesfor a CCE aggregation level L in control resource set p and at PDCCHmonitoring period k_(p). Otherwise, M_(p,max) ^((L)) can be the maximumnumber of PDCCH candidates among all configured DCI formats over allconfigured n_(CI) values and over all overlapping PDCCH monitoringperiods for a CCE aggregation level L in control resource set p.

A UE configured to monitor PDCCH candidates in a given serving cell witha given DCI format size with carrier indicator field, and CRC scrambledby C-RNTI, where the PDCCH candidates can have one or more possiblevalues of carrier indicator field for the given DCI format size, canassume that an PDCCH candidate with the given DCI format size can betransmitted in the given serving cell in any PDCCH UE specific searchspace corresponding to any of the possible values of carrier indicatorfield for the given DCI format size.

Using a same DMRS for PDCCH and PDSCH demodulation is generally notpossible as a PDCCH transmission scheme can be different from a PDSCHtransmission scheme and a PDCCH transmission bandwidth can be differentfrom a PDSCH transmission bandwidth. For example, a PDCCH transmissionto a UE can be without spatial multiplexing of layers and in a firstbandwidth while a PDSCH transmission to a UE can be with spatialmultiplexing of layers and in a second bandwidth.

To reduce overhead associated with a first DMRS transmission for PDCCHdemodulation and with a second DMRS transmission for PDSCH demodulation,particularly for transmission of small data transport block sizes thattypically do not benefit from spatial multiplexing of layers, a UE canassume a same transmission scheme for PDCCH transmission and for PDSCHtransmission. Further, a PDCCH transmission bandwidth can be included ina PDSCH transmission bandwidth.

FIG. 13 illustrates an example PDCCH transmission and PDSCH transmission1300 using a same DMRS for demodulation according to embodiments of thepresent disclosure. An embodiment of the PDCCH transmission and PDSCHtransmission 1300 shown in FIG. 13 is for illustration only. One or moreof the components illustrated in FIG. 13 can be implemented inspecialized circuitry configured to perform the noted functions or oneor more of the components can be implemented by one or more processorsexecuting instructions to perform the noted functions. Other embodimentsare used without departing from the scope of the present disclosure.

As shown in FIG. 13, a PDCCH transmission is over a first OFDM symboland a PDSCH transmission in over a first and second OFDM symbols 1310.The PDCCH transmission is over a number of RBs that is a subset of anumber of RBs for the PDSCH transmission. For example, the RBs for thePDCCH transmission can be the center C RBs of the D≥C RBs for the PDSCHtransmission. The PDCCH RBs 1320 and the PDSCH RBs in the first OFDMsymbol include sub-carriers used for DMRS transmission in addition tosub-carriers used for transmission of control information and datainformation, respectively. For example, one sub-carrier every threesub-carriers can be used for DMRS transmission. The PDSCH RBs 1340 inthe second OFDM symbol do not include any sub-carriers used for DMRStransmission. For demodulation of a PDCCH transmission or of a PDSCHtransmission, a UE can filter the DMRS sub-carriers in both the RBs usedfor PDSCH transmission and the RBs used for PDCCH transmission in thefirst symbol.

This also reduces UE computational complexity and power consumption asthe UE needs to obtain only one channel estimate to demodulate a PDCCHtransmission and a PDSCH transmission. In order for the DMRS filteringacross the RBs in the first OFDM symbol to result to a valid channelestimate, the DMRS needs to use a same precoding across all RBs in thefirst OFDM symbol and the same precoding also needs to be used for thePDCCH transmission and for the PDSCH transmission. For example, both thePDCCH transmission and the PDSCH transmission can be based on a sametransmitter diversity scheme. For example, both the PDCCH transmissionand the PDSCH transmission can be based on the use of a same precodingfor beam-formed transmissions.

As a DMRS can be power boosted to improve channel estimation, it can bebeneficial to avoid placing DMRS transmission in neighboring cells onsame sub-carriers of a same slot symbol as, otherwise, usefulness froman increase in DMRS transmission power may be largely nullified due tomutual interference of among power boosted DMRS. Therefore, a location(sub-carriers) used for a DMRS transmission in an RB can bepseudo-random or indicated by a gNB for example through an associationwith a synchronization signal sequence used by the gNB. A pseudo-randomdetermination can be based on an identity of a cell where a DMRS istransmitted.

For example, for a DMRS transmission from an antenna port over 4 equallyspaced sub-carriers in an RB of 12 sub-carriers, the sub-carriers withDMRS transmission in the RB can be determined as k_(DMRS)=3k+δ_(shift)mod 3 where k=0, 1, 2, 3 and δ_(shift)=N_(ID) ^(cell) mod 3 where N_(ID)^(cell) is the cell ID that a UE obtains from the initialsynchronization process with the cell. For example, for a DMRStransmission from an antenna port over 2 equally spaced sub-carriers inan RB of 12 sub-carriers, the sub-carriers with DMRS transmission in theRB can be determined as k_(DMRS)=6k+δ_(shift) mod 6 where k=0, 1 andδ_(shift)=N_(ID) ^(cell) mod 6. An indication by a gNB can be based on asequence used to transmit a synchronization signal such as a primarysynchronization signal or a secondary synchronization signal.

When distributed PDCCH transmissions and localized PDCCH transmissionscan be multiplexed in a same DL control resource set, the distributedPDCCH transmission can be based on transmission diversity scheme usingprecoder cycling where, in some RBs, the precoder can also be associatedwith a localized PDCCH transmission. In such case, a UE cannot assumethat a DMRS in a PRB uses a same precoder in different slots or infrequency contiguous RBs and cannot utilize the DMRS for time trackingor frequency tracking.

To circumvent the above limitation for a UE to use a DMRS associatedwith demodulation of PDCCH transmissions for time tracking and forfrequency tracking, the UE can be informed in advance that the DMRS usesa same precoding in predetermined slots or in predetermined RBs (withDMRS transmission). The predetermined slots or the predetermined RBs canbe defined in a system operation, such as for example every slot every 5msec or all RBs of a DL control resource set, or can be signaled bysystem information. For example, the predetermined slots or thepredetermined RBs can be determined to be the ones where a gNB transmitsa PDCCH scheduling a first system information block. Based on theassumption that the DMRS transmission in the predetermined RBs of a DLcontrol resource set and in the predetermined slots uses a sameprecoding, a UE can use the DMRS to perform time tracking or frequencytracking in addition to channel estimation.

For a PDCCH transmission diversity scheme using precoder cycling, theprecoder weights can be specified per bundle of N_(bundle) contiguousRBs. For example, for N_(total)=4·N_(bundle) and two transmitterantennas, a precoder in the first N_(bundle) of RBs can be {1;1}, aprecoder in the second N_(bundle) of RBs can be {1;−1}, a precoder inthe third N_(bundle) of RBs can be {1;j}, and a precoder in the fourthN_(bundle) of RBs can be {1;−j}. By knowing the precoder applied in eachbundle of RBs, a UE can remove the precoding and obtain a non-precodedDMRS reception over the N_(total) RBs. The non-precoded DMRS can be usedfor other purposes such as wideband channel estimation or time trackingwhen received at different time instances.

FIG. 14 illustrates an example operation 1400 for a UE to assume a sameDMRS precoding in predetermined slots and in predetermined RBs of a DLcontrol resource set according to embodiments of the present disclosure.An embodiment of the operation 1400 shown in FIG. 14 is for illustrationonly. One or more of the components illustrated in FIG. 14 can beimplemented in specialized circuitry configured to perform the notedfunctions or one or more of the components can be implemented by one ormore processors executing instructions to perform the noted functions.Other embodiments are used without departing from the scope of thepresent disclosure.

As shown in FIG. 14, a gNB transmits DMRS in a DL control resource set1410. The UE receives the DMRS 1420 and determines whether or not it canassume a fixed DMRS precoding in the slot 1430. The determination can bebased on a predetermined slot periodicity or in a pattern of slotssignaled by system information from the gNB, for example using a bit-mapthat is periodically repeating in time. The RBs can include all RBs withDMRS transmission in the DL control resource set or can be signaled bythe gNB using higher layer signaling.

For example the RBs can be the ones used for PDCCH transmissions in acommon search space when the RBs associated with a common search spaceare not all RBs in a DL control resource set. Also, when a UE isconfigured multiple DL control resource sets, the RBs can be the ones ina first DL control resource set that can also include transmission ofUE-group common DL control signaling in a slot. When the UE cannotassume a fixed DMRS precoding in the slot, the UE may not use the DMRSreceived in the slot for time tracking or for frequency tracking 1440.When the UE can assume a fixed DMRS precoding in the slot, the UE canuse the DMRS received in the slot for time tracking or for frequencytracking 1450.

Several transmission schemes can exist for a PDSCH transmission of for aPUSCH transmission. When a transmission scheme is configured by higherlayer signaling, a UE can monitor a DCI format that includes onlynecessary fields for the transmission scheme and different DCI formatscan be associated with different transmission schemes.

Although offering operational simplicity, a semi-static configuration ofa transmission scheme for a PDSCH or a PUSCH is disadvantageous as itdoes not enable a gNB to quickly adapt a transmission scheme for a UE,for example based on variations of a channel medium experienced by theUE, and instead needs to rely on a reconfiguration by higher layersignaling. When dynamic adaptation among a set of multiple transmissionschemes is based on a use of a set of respective multiple DCI formatshaving respective multiple sizes, a UE needs to decode each of themultiple DCI formats in each slot to determine a transmission schemeused for a respective PDSCH transmission or PUSCH transmission and thisincreases a number of decoding operations the UE needs to perform perslot, for example by a factor equal to the number of multiple DCIformats with different sizes. Instead, a single DCI format that includesa flag indicating a respective transmission scheme can be used in orderfor a UE to decode a single DCI format per slot.

The tradeoff for the reduced number of decoding operation is anoccasional unnecessary overhead when scheduling of a PDSCH transmissionor PUSCH transmission with a transmission scheme does not require allfields in the DCI format or requires fields with reduced number of bits.Transmission schemes that can be associated with a single DCI format canbe ones requiring a similar number of bits, such as at most 20% fewerbits than the transmission scheme that requires the largest number ofbits and is the one that determines the size of the DCI format.

To reduce an overhead associated with an introduction of a flag in a DCIformat that can indicate multiple transmission schemes, such as morethan two transmission schemes, the flag can have a nested structure andinclude only one additional bit relative to the number of bits requiredfor scheduling a PDSCH transmission or a PUSCH transmission with atransmission scheme, referred to as first transmission scheme, requiringthe largest number of bits in the DCI format.

The flag is located at the beginning of the DCI format. A UE can firstexamine the value of the binary flag. When the flag value is a firstvalue, the UE can determine that the transmission scheme of anassociated PDSCH or PUSCH transmission is the first transmission scheme.When the flag value is a second value, the UE can determine a number ofadditional bits in the DCI format that are not use for schedulingassociated with the first transmission scheme and can serve as anextended flag. For example, a location of the additional bits when theflag value is the second value can be after the flag or can be at theend of the DCI format (last bits of the DCI format). For example, whenthere are two less bits required for the second transmission scheme withthe second largest number of required bits in the DCI format, relativeto the first transmission scheme, the value of the two bits can be usedto indicate whether the DCI format schedules a respective PDSCH or PUSCHtransmission with a second, third, fourth, or fifth, when any,transmission scheme.

FIG. 15 illustrates an example operation 1500 for a DCI format thatinclude a binary flag to indicate a transmission scheme, among multipletransmission schemes, for a PDSCH transmission or a PUSCH transmissionaccording to embodiments of the present disclosure. An embodiment of theoperation 1500 shown in FIG. 15 is for illustration only. One or more ofthe components illustrated in FIG. 15 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

As shown in FIG. 15, a gNB transmits to a UE a DCI format that includesa “flag” field through a PDCCH 1510. The UE detects the DCI format 1520and determines whether or not a value for the “flag” field is equal to“1” 1530. When it is not, the UE receives an associated PDSCHtransmission or a PUSCH transmission with first respective transmissionscheme 1540. When it is, the UE determines whether or not a value for anadditional bit, that is included in the DCI format for scheduling withthe first transmission scheme but is not used for scheduling with anyother transmission scheme, is equal to “1” 1550. When it is not, the UEreceives an associated PDSCH transmission or a PUSCH transmission withsecond respective transmission scheme 1560; otherwise, the UE receivesan associated PDSCH transmission or a PUSCH transmission with thirdrespective transmission scheme 1570.

A predetermined DCI format transmitted in a UE-specific search space,such as a first DCI format (fallback DCI format) monitored by a UE thathas a smaller size than a second DCI format (non-fallback DCI format)monitored by the UE, can be used to provide fallback operation duringtime periods where parameters for transmissions to or from the UE arereconfigured by a gNB. For example, a DCI format scheduling a PDSCHtransmission to a UE can include a field indicating a slot offset,including symbols within the slot, or a field indicating a resource fora PUCCH transmission by the UE in response to a reception of dataconveyed by the PDCCH.

A UE can be configured by higher layers a set of slot offsets or a setof PUCCH resources and respective fields can indicate a value from arespective set. During a time period associated with a reconfigurationof values in one or more such sets of values or prior to a configurationby UE-specific higher layer signaling of values in such sets of values,a UE can use values indicated by UE-group common system information. AUE can determine whether to either use values signaled by UE-groupcommon higher layer signaling (system use values signaled by UE-specifichigher layer signaling based on an associated DCI format and the UE canuse the former values when the UE detects a first DCI format, such as afallback DCI format, and use the latter values when the UE detects asecond DCI format, such as a non-fallback DCI format.

The DCI formats can also be same and be differentiated by a flag valueas described in FIG. 15. For example, a flag value can correspond to useof parameter values, such as a HARQ-ACK transmission timing offset or aPUCCH resource for a HARQ-ACK transmission, or a slot timing offset fora PDSCH or PUSCH transmission relative to a slot of a transmission foran associated DCI format, that are signaled to a UE by UE-common higherlayer signaling. Therefore a flag field in a DCI format, in addition toproviding a differentiation of transmission schemes for an associatedPDSCH transmission or PUSCH transmission, can also providedifferentiation for an interpretation of values for other fields in theDCI format according to values configured by either UE-common higherlayer signaling or by UE-specific higher layer signaling.

To improve flexibility in a system operation and reliability for PDCCHtransmissions, a number of CCE aggregation levels and a number ofcandidates per CCE aggregation level for a UE to monitor in a commonsearch space can be configured by system information from a gNB. Forexample, a first system information block can indicate a number of CCEaggregation levels and a number of candidates per CCE aggregation levelfor PDCCH transmissions, for example scheduling a random accessresponse, paging, or used for transmission of UE-group commoninformation such as transmit power control commands, in the CSS. Thefirst system information block can be scheduled with a CCE aggregationlevel from a predetermined set of one or more CCE aggregation levels orthe aggregation level for scheduling a transmission for the firstinformation block can be implicitly or explicitly indicated in a masterinformation block.

An important objective in the design of a PDCCH search space is areduction in a number of channel estimations a UE needs to perform inorder to decode PDCCH candidates as this can directly reduce a requiredpower consumption of a UE modem for decoding PDCCH candidates in eachslot. This power consumption can correspond to a significant percentage,such as about 50%, of the total UE modem power consumption as a UE needsto decode PDCCH in every DL slot, even when the UE is not scheduled DLreceptions or UL transmissions, when the UE is not in a discontinuousreception (DRX) state. A nested structure for a PDCCH search space isone approach for reducing a number of channel estimations where achannel estimate obtained for decoding a PDCCH candidate with a firstCCE aggregation level can be used for decoding a PDCCH candidate with asecond CCE aggregation level that is smaller than the first CCEaggregation level that can typically correspond to the largest CCEaggregation level.

FIG. 16 illustrates an example nested structure of PDCCH candidates 1600according to embodiments of the present disclosure. An embodiment of thenested structure of PDCCH candidates 1600 shown in FIG. 16 is forillustration only. One or more of the components illustrated in FIG. 16can be implemented in specialized circuitry configured to perform thenoted functions or one or more of the components can be implemented byone or more processors executing instructions to perform the notedfunctions. Other embodiments are used without departing from the scopeof the present disclosure.

As shown in FIG. 16, in a PRB set, or over an entire system BW, a UE isconfigured with M⁽⁸⁾=2 candidates 1610, 1615 for an aggregation level ofL=8 CCEs, M⁽⁴⁾=2 candidates 1620 for an aggregation level of L=4 CCEs,M⁽²⁾=6 candidates 1630, 1635 for an aggregation level of L=2 CCEs, andM⁽¹⁾=6 candidates 1640 for an aggregation level of L=1 CCE. CCE indexesfor the M⁽⁸⁾=2 candidates with L=8 CCEs can be consecutive as inequation 1 or non-consecutive with a defined offset as in equation 2.CCE indexes for lower CCE aggregation levels are a subset of CCE indexesfor the M⁽⁸⁾=2 candidates with L=8 CCEs. CCE indexes for lower CCEaggregation levels can have consecutive indexes starting from the indexof the first CCE of the first candidate of the M⁽⁸⁾=2 candidates withL=8 CCEs, as shown in FIG. 16, or can be equally divided to occupy CCEsindexes of each of the M⁽⁸⁾=2 candidates with L=8 CCEs, and so on.

A drawback of using a nested structure for CCE indexes, as for examplein FIG. 16, is an increase in a probability that a PDCCH to a UE cannotbe transmitted because associated CCEs have at least partiallyoverlapping indexes with CCEs used for a PDCCH transmission to anotherUE. For example, when CCEs for PDCCH transmission to a first UE and CCEsfor PDCCH transmission to a second UE overlap for candidates using thelargest CCE aggregation level, it is likely that such overlapping existsfor PDCCH candidates using smaller CCE aggregation levels and when aPDCCH transmission to the first UE is with the largest CCE aggregationlevel, there may be few candidates and only with small CCE aggregationlevels available for PDCCH transmission to the second UE.

For example, with reference to FIG. 16, when a first PDCCH transmissionto a first UE needs to use the CCEs of the first of the M⁽⁴⁾=2candidates with L=4 CCEs, and the CCEs for the first PDCCH candidatewith L=8 CCEs fully overlap with those for a first PDCCH candidate withL=8 CCEs for a second UE, a PDCCH transmission to the second UE cannotuse most remaining candidates for any CCE aggregation level. An increasein a blocking probability can substantially negate potential benefits ofa nested search space structure for UE power consumption as the UE needsto remain active for a longer time period to complete transmissions orreceptions of data.

CCEs for a PDCCH transmission can be formed by a number of REGs whereone REG is same as one RB over one OFDM symbol. Assuming that a CCE is aminimum resource unit for a DCI format transmission with a given coderate and QPSK modulation, a number of REGs required for a CCE depends ona reference DCI format size and on a number of SCs in an RB that can beused for transmission of the DCI format (SCs used for DMRS transmissionare excluded). For example, for a DCI format size of 60 bits (or 76 bitsincluding a CRC of 16 bits) and for a code rate of ⅔, the DCI formattransmission requires 57 SCs. For 2 DMRS SCs per RB used for PDCCHtransmission and for 12 SCs per RB, a number of about 6 REGs (or 6 RBs)is needed for a CCE. For 4 DMRS SCs per RB used for PDCCH transmissionand for 12 SCs per RB, a number of about 7 REGs (or 7 RBs) is needed fora CCE. A PDCCH transmission can be over variable number of OFDM symbols,such as 1, 2, or 3 OFDM symbols.

The number of symbols can be configured by signaling from the physicallayer or from higher layers. To improve spectral efficiency and simplifya design for PDCCH transmissions, design targets in mapping CCEs to REGsor PDCCHs to CCEs can include enabling a multiplexing of distributedPDCCH transmissions and localized PDCCH transmissions in a same PRB set(or control resource set) or enabling all CCEs to be equivalent in termsof SCs available for a PDCCH transmission regardless of whether thePDCCH transmission spans one OFDM symbol or spans multiple OFDM symbols.

Therefore, there is a need to design nested PDCCH search spacestructures for distributed PDCCH transmissions and for localized PDCCHtransmissions.

There is another need to design nested PDCCH search space structureswith reduced PDCCH blocking probability.

There is another need to define mapping for CCEs to REGs and for PDCCHsto CCEs for a nested PDCCH search space over multiple slot symbols.

In one embodiment, designs for a nested PDCCH search space and designsthat enable reductions in a blocking probability for PDCCH candidates ofvarious CCE aggregation levels in a nested PDCCH search space areconsidered.

For PDCCH transmission, an associated blocking probability benefits fromPDCCH candidates for different CCE aggregation levels typically usingdifferent CCE indexes. For example, for a PDCCH search space defined asin equation 1. CCE indexes for a PDCCH candidate not only depend on arespective CCE aggregation level L but also on a number of candidatesM_(p) ^((L)) per CCE aggregation level L.

For a nested search space, flexibility in CCE indexes for a PDCCHcandidate according to equation 1 is materially diminished as CCEindexes need to be common among multiple PDCCH candidates with differentCCE aggregation levels. Additionally, based on equation 1, CCE indexesfor different PDCCH candidates with a same CCE aggregation level aredeterministic. For example, for a PDCCH search space according toequation 1, CCE indexes for PDCCH candidates with a same CCE aggregationlevel are offset by a deterministic factor

$\lfloor \frac{N_{{CCE},p,k}}{L \cdot M_{p}^{(L)}} \rfloor {( {{modulo}\mspace{14mu} \lfloor {N_{{CCE},p,k}/L} \rfloor} ).}$

Therefore, when CCE indexes for PDCCH candidates overlap for differentUEs and a nested search space structure is used, a probability that alarge number of PDCCH candidates for any CCE aggregation level overlapis materially increased and a blocking probability for PDCCHtransmissions to such UEs is consequently increased. In the following,it is generally assumed that CCE aggregation levels can also depend on aPRB set, also referred to as control resource set, that a UE isconfigured for PDCCH receptions and a notation L_(p) (instead of L) isused. Further, it is assumed that a CCE aggregation level L_(p) is apower of 2 such as L_(p)=2_(n), n=0, 1, 2, . . . .

A first realization considers that CCE indexes for PDCCH candidates withCCE aggregation levels that are smaller than a maximum one in a controlresource set are determined relative to CCE indexes for PDCCH candidateswith the largest CCE aggregation level in the control resource set.

A first mechanism for reducing a blocking probability of PDCCHtransmissions to different UEs is to randomize CCE indexes for PDCCHcandidates with a largest CCE aggregation level by having adetermination for the parameter Y_(p,k) in equation 1 depend on an indexof a PDCCH candidate in addition to a UE RNTI. Then, for example, whenCCE indexes for a PDCCH candidate with a largest CCE aggregation leveloverlap for two UEs, a probability of such overlapping for additionalPDCCH candidates with the largest CCE aggregation level is reduced dueto the randomization of respective CCE indexes according to UE RNTI.

For example, for CCE indexes determined according to equation 1 and forM_(p) ^((L) ^(p,max) ⁾ PDCCH candidates with the largest CCE aggregationlevel, CCE indexes for candidate 0≤m≤M_(p) ^((L) ^(p,max) ⁾−1 can bedetermined as in equation 2:

$\begin{matrix}{{{L_{p,{{ma}\; x}}\{ {( {Y_{p,k,m} + \lfloor \frac{m \cdot N_{{CCE},p,k}}{L_{p,{{ma}\; x}} \cdot M_{p}^{(L_{p,{{ma}\; x}})}} \rfloor} ){mod}\lfloor {N_{{CCE},p,k}/L_{p,{{ma}\; x}}} \rfloor} \}} + i},{i = 0},{{\ldots \mspace{14mu} L_{p,{{ma}\; x}}} - 1}} & {{equation}\mspace{14mu} 2}\end{matrix}$

where a same notation as in equation 1 applies andY_(p,k,m)=(A_(p,m)·Y_(p,k−1,m))mod D provides randomization fordifferent candidates with the largest CCE aggregation level. Forexample, Y_(p,−1,m)=n_(RNRI)≠0 and, for M_(p) ^((L) ^(max) ⁾=2,A_(p,0)=39827 and A_(p,1)=39831.

A second mechanism for reducing a blocking probability of PDCCHtransmissions to different UEs is to randomize CCE indexes for PDCCHcandidates by having a random offset between last (or first) CCE indexesof successive PDCCH candidates. The random offset can be a function ofthe UE RNTI or of both the UE RNTI and of a PDCCH candidate index.

For example, for CCE indexes determined according to equation 1 andM_(p) ^((L) ^(p) ^(,max)) PDCCH candidates with the largest CCEaggregation level, CCE indexes for candidate 0≤m≤M_(p) ^((L) ^(p)^(,max))−1 can be determined as in equation 3A or equation 3A:

$\begin{matrix}{{{L_{p,{{ma}\; x}}\{ {( {Y_{p,k,m} + \lfloor \frac{m \cdot N_{{CCE},p,k}}{L_{p,{{ma}\; x}} \cdot M_{p}^{(L_{{ma}\; x})}} \rfloor + {f(m)}} ){mod}\lfloor {N_{{CCE},p,k}/L_{p,{{ma}\; x}}} \rfloor} \}} + i},{i = 0},{{{\ldots \mspace{14mu} L_{p,{{ma}\; x}}} - 1};{and}}} & {{equation}\mspace{14mu} 3A} \\{{{L_{p,{{ma}\; x}}\{ {( {Y_{p,k,m} + \lfloor \frac{{f(m)} \cdot N_{{CCE},p,k}}{L_{p,{{ma}\; x}} \cdot M_{p}^{(L_{p,{{ma}\; x}})}} \rfloor} ){mod}\lfloor {N_{{CCE},p,k}/L_{p,{{ma}\; x}}} \rfloor} \}} + i},{i = 0},{{\ldots \mspace{14mu} L_{p,{{ma}\; x}}} - 1}} & {{equation}\mspace{14mu} 3B}\end{matrix}$

where a same notation as in equation 1 applies and f(m) is apseudo-random function having as arguments the PDCCH candidate m and theUE RNTI n_(RNTI)≠0, for example f(m)=m·n_(RNRI).

The first mechanism (different hashing function for different PDCCHcandidates) and the second mechanism (UE-specific offset betweensuccessive PDCCH candidates) can also be combined.

In equation 2 or in equations 3A/3B, as CCE indexes for different PDCCHcandidates with a same CCE aggregation level are random, and are notseparated by a predetermined offset as in equation 1, overlapping canoccur. When CCE indexes for different PDCCH candidates with a same CCEaggregation level at least partially overlap for values of Y_(p,k,m) inslot k, when for example they are determined based on equation 2,adjustments can apply to avoid such overlapping.

For example, when CCE indexes for different PDCCH candidates overlap, aUE can re-use CCE indexes determined in a last slot when CCE indexes fordifferent PDCCH candidates did not overlap. For example, when CCEindexes for different PDCCH candidates overlap, CCE indexes for eachapplicable PDCCH candidate after the first one can be shifted by arespective minimum value to avoid overlapping with previous PDCCHcandidates for a same CCE aggregation level. It is also possible foroverlapping of CCE indexes to be allowed to occur.

After determining CCE indexes in a control resource set p for PDCCHcandidates with a largest CCE aggregation level, a next step is todetermine CCE indexes for PDCCH candidates with CCE aggregation levelsthat are smaller than the largest CCE aggregation level in the controlresource set p.

In some embodiments of case 1 for M_(p) ^((L) ^(p) ⁾·L_(p)≤M_(p) ^((L)^(p,max) ⁾·L_(p,max), when a condition M_(p) ^((L) ^(p) ⁾·L_(p)≤M_(p)^((L) ^(p,max) ⁾·L_(p,max) holds for any CCE aggregation levelL_(p)<L_(p,max), CCE indexes for all PDCCH candidates with CCEaggregation level L_(p) can be a subset of CCE indexes for all PDCCHcandidates with CCE aggregation level L_(p,max).

A first approach for determining CCE indexes for PDCCH candidates withCCE aggregation level L_(p)<L_(p,max) considers a substantially equaldistribution for a total of M_(p) ^((L) ^(p) ⁾ PDCCH candidates with CCEaggregation level L_(p)<L_(p,max) among the CCE indexes of each of theM_(p) ^((L) ^(p,max) ⁾ PDCCH candidates with CCE aggregation levelL_(p,max). CCE indexes for first M_(p,0) ^((L) ^(p) ⁾=┌M_(p) ^((L) ^(p)⁾/M_(p) ^((L) ^(p,max) ⁾┐ candidates with CCE aggregation level L_(p)area subset of CCE indexes for a first PDCCH candidate with CCEaggregation level L_(p,max). When, M_(p) ^((L) ^(p,max) ⁾−1>0, CCEindexes for second M_(p,1) ^((L) ^(p) ⁾=┌M_(p) ^((L) ^(p) ⁾−┌M_(p) ^((L)^(p) ⁾/M_(p) ^((L) ^(p,max) ⁾┐)/(M_(p) ^((L) ^(p,max) ⁾−1)┐ PDCCHcandidates with CCE aggregation level L_(p) are a subset of CCE indexesfor a second PDCCH candidate with CCE aggregation level L_(p,max). WhenM M_(p) ^((L) ^(p,max) ⁾−2>0 CCE indexes for third M_(p,2) ^((L) ^(p)⁾=┌M_(p) ^((L) ^(p) ⁾−(M_(p) ^((L) ^(p) ⁾−┌M_(p) ^((L) ^(p) ⁾/M_(p)^((L) ^(p,max) ⁾┐)/(M_(p) ^((L) ^(p,max) ⁾−1))/(M_(p) ^((L) ^(p,max)⁾−2)┐ PDCCH candidates with CCE aggregation level L_(p) are a subset ofCCE indexes for a third PDCCH candidate with CCE aggregation levelL_(p,max), and so on. In general, when M_(p) ^((L) ^(p,max) ⁾−m+1>0, CCEindexes for m-th M_(p,m) ^((L) ^(p) ⁾=┌M_(p) ^((L) ^(p) ⁾−( . . . −M_(p)^((L) ^(p) ⁾−┌M_(p) ^((L) ^(p) ⁾/M_(p) ^((L) ^(p,max) ⁾┐)/(M_(p) ^((L)^(p,max) ⁾−1))/ . . . )/(M_(p) ^((L) ^(p,max) ⁾−m+1)┐ PDCCH candidateswith CCE aggregation level L_(p) are a subset of CCE indexes for a PDCCHcandidate with CCE aggregation level L_(p,max).

After determining M_(p,m) ^((L) ^(p) ⁾ PDCCH candidates for CCEaggregation level L_(p), a determination of CCE indexes for respectivePDCCH candidates can be as in equation 1 where N_(ECCE,p,k) is replacedby L_(p,max). Then, CCE indexes for 0≤{tilde over (m)}≤M_(p,m) ^((L)^(p) ⁾−1 PDCCH candidates can be determined as in equation 4:

$\begin{matrix}{{{L_{p} \cdot \lbrack {( {Y_{p,k} + \lfloor \frac{\overset{\sim}{m} \cdot L_{p,{{ma}\; x}}}{L_{p} \cdot M_{p,m}^{(L_{p})}} \rfloor} ){mod}\lfloor {L_{p,{{ma}\; x}}/L_{p}} \rfloor} \}} + i},{i = 0},{{\ldots \mspace{14mu} L_{p}} - 1.}} & {{equation}\mspace{14mu} 4}\end{matrix}$

In equation 4, it is also possible to use Y_(p,k,m) instead of Y_(p,k).

A randomization of CCE indexes PDCCH candidates with CCE aggregationlevel L_(p,max) can also extend to CCE indexes for PDCCH candidates withCCE aggregation level L_(p)<L_(p,max) as in equation 2 or in equations3A/3B where instead of considering all CCE indexes N_(ECCE,p,k) of aPDCCH resource set, only CCE indexes for a respective PDCCH candidatewith CCE aggregation level L_(p,max) are considered.

FIG. 17 illustrates an example process for determining CCEs 1700 forPDCCH candidates based on a first realization for a nested PDCCH searchspace structure according to embodiments of the present disclosure. Anembodiment of the process for determining CCEs 1700 shown in FIG. 17 isfor illustration only. One or more of the components illustrated in FIG.17 can be implemented in specialized circuitry configured to perform thenoted functions or one or more of the components can be implemented byone or more processors executing instructions to perform the notedfunctions. Other embodiments are used without departing from the scopeof the present disclosure.

As shown in FIG. 17, a UE is configured by a gNB a control resource setp having a number of N_(CCE,p,k) CCEs, and a number of M_(p) ^((L) ^(p)⁾ PDCCH candidates with CCE aggregation level L_(p) in the controlresource set p. It is also possible that values of M_(p) ^((L) ^(p) ⁾and L_(p) for possible values of N_(CCE,p,k) are determined in thespecifications of a system operation or are derived by the UE accordingto some specified formula. The UE determines CCE indexes for PDCCHcandidate m, 0≤m≤M_(p) ^((L) ^(p,max) ⁾−1, with CCE aggregation levelL_(p,max) as

${{L_{p,{{ma}\; x}}\{ {( {Y_{p,k,m} + \lfloor \frac{m \cdot N_{{CCE},p,k}}{L_{p,{{ma}\; x}} \cdot M_{p}^{(L_{{ma}\; x})}} \rfloor + {f(m)}} ){mod}\lfloor {N_{{CCE},p,k}/L_{p,{{ma}\; x}}} \rfloor} \}} + i},{i = 0},{{\ldots \mspace{14mu} L_{p,{{ma}\; x}}} - 1},$

where f(m) is a function of PDCCH candidate m and can also be set to 01710. The UE determines M_(p,m) ^((L) ^(p) ⁾ PDCCH candidates with CCEindexes that are a subset of CCE indexes for PDCCH candidate m,0≤m≤M_(p) ^((L) ^(p,max) ⁾−1 1720. From the set of CCEs for PDCCHcandidate m with L_(p,max), the UE determines CCE indexes for PDCCHcandidate {tilde over (m)}, 0≤{tilde over (m)}≤M_(p,m) ^((L) ^(p) ⁾−1,with

${L_{p} < L_{p,{{ma}\; x}}},{{{as}\mspace{14mu} {L_{p} \cdot \{ {( {Y_{p,k} + \lfloor \frac{\overset{\sim}{m} \cdot L_{p,{{ma}\; x}}}{L_{p} \cdot M_{p,m}^{(L_{p})}} \rfloor} ){mod}\lfloor {L_{p,{{ma}\; x}}/L_{p}} \rfloor} \}}} + i},{i = 0},{{\ldots \mspace{14mu} L_{p}} - {1\mspace{14mu} 1730.}}$

FIG. 18 illustrates an example determination of CCEs 1800 for PDCCHcandidates based on a first approach of a first realization for a nestedPDCCH search space structure according to embodiments of the presentdisclosure. An embodiment of the determination of CCEs 1800 shown inFIG. 18 is for illustration only. One or more of the componentsillustrated in FIG. 18 can be implemented in specialized circuitryconfigured to perform the noted functions or one or more of thecomponents can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

As shown in FIG. 18, a UE is configured to decode PDCCH candidates forfour CCE aggregation levels corresponding 1, 2, 4, and 8 CCEs. It isM_(p) ⁽⁸⁾=M_(p) ^((L) ^(p,max) ⁾=2, M_(p) ⁽⁴⁾=3, M_(p) ⁽²⁾=6, and M_(p)⁽¹⁾=4. The UE determines a first set and a second set of CCE indexes fora first PDCCH candidate 1810 and a second PDCCH candidate 1815 of theM_(p) ⁽⁸⁾=2 candidates, respectively (e.g., equations 2 through 4 canapply as exemplary reference). PDCCH candidates M_(p) ^((L) ^(p) ⁾,L_(p)<L_(p,max), are equally distributed (when M_(p) ^((L) ^(p) ⁾ is aneven number) to use CCE indexes from the CCE indexes of either the firstPDCCH candidate with CCE aggregation level L_(p,max) 1820, 1830, and1840, or the second PDCCH candidate with CCE aggregation level L_(p,max)1825, 1835, and 1845.

A second approach for determining CCE indexes for PDCCH candidates withCCE aggregation level L_(p)<L_(p,max) considers configuration for adistribution for a total of M_(p) ^((L) ^(p) ⁾ PDCCH candidates with CCEaggregation level L_(p)<L_(p,max) among CCE indexes for each of theM_(p) ^((L) ^(p,max) ⁾ PDCCH candidates with CCE aggregation levelL_(p,max). The configuration can be provided by a gNB through higherlayer signaling. For example, for M_(p) ^((L) ^(p,max) ⁾=2 and 2·M_(p)^((L) ^(p) ⁾·L_(p)≤3·L_(p,max), a configuration can indicate that CCEindexes for ⅔ of the M_(p) ^((L) ^(p) ⁾ PDCCH candidates with CCEaggregation level L_(p) are a subset of CCE indexes for a first PDCCHcandidate with CCE aggregation level L_(p,max) and that CCE indexes for⅓ of the M_(p) ^((L) ^(p) ⁾ PDCCH candidates with CCE aggregation levelL_(p) are a subset of the CCE indexes for a second PDCCH candidate withCCE aggregation level L_(p,max).

The second approach enables a gNB to have additional control over ablocking probability for UEs with an RNTI that can otherwise lead toincreased blocking probability particularly when a total number of CCEsN_(ECCE,p,k) in control resource set p is not large enough and can leadto overlapping of CCEs for different PDCCH candidates with CCEaggregation level L_(p,max).

The aforementioned determinations, according to the first realization,of CCE indexes for PDCCH candidates with different CCE aggregationlevels consider that M_(p) ^((L) ^(p) ⁾·L_(p)≤M_(p) ^((L) ^(p,max)⁾·L_(p,max) for all L_(p)<L_(p,max). To simplify a determination of CCEindexes for a nested structure of PDCCH candidates, M_(p) ^((L) ^(p)⁾·L_(p)≤M_(p) ^((L) ^(p,max) ⁾·L_(p,max) can be assumed when a nestedPDCCH structure is used according to the first realization and a UE caneither disregard configurations for numbers of PDCCH candidates forrespective CCE aggregation levels that do not satisfy that condition orassume a minimum number of additional virtual candidates for L_(p,max)so that M_(p) ^((L) ^(p) ⁾·L_(p)≤M_(p) ^((L) ^(p,max) ⁾·L_(p,max). A UEcan also be separately configured by higher layers whether to assume anested structure for CCEs of PDCCH candidates for different aggregationlevels and accordingly determine search space equations for CCE indexesof PDCCH candidates. A CCE structure for a UE-common search space can bedefined to have a conventional structure (search space) or a nestedstructure in the specifications of the system operation.

In some embodiments of case 2 for M_(p) ^((L) ^(p) ⁾·L_(p)>M_(p) ^((L)^(p,max) ⁾·L_(p,max) for at least one L_(p)<L_(p,max), when a systemoperation allows for M_(p) ^((L) ^(p) ⁾·L_(p)>M_(p) ^((L) ^(p,max)⁾·L_(p,max) for at least one CCE aggregation level L_(p,max1)<L_(p,max)such as L_(p,max)=8 and L_(p,max1)=4, CCE indexes for a number of PDCCHcandidates M_(p,rem) ^((L) ^(p,max1) ⁾=M_(p) ^((L) ^(p,max1) ⁾−M_(p)^((L) ^(p,max) ⁾·L_(p,max)/L_(p,max1) with CCE aggregation levelL_(p,max1) can be determined independently of CCE indexes for PDCCHcandidates with CCE aggregation level L_(p,max) and are not a subset ofthe latter CCE indexes while CCE indexes for M_(p) ^((L) ^(p,max)⁾·L_(p,max)/L_(p,max1) PDCCH candidates with CCE aggregation levelL_(p,max1) can be determined as when it is M_(p,max1) ^((L) ^(p,max)⁾·L_(p,max1)≤M_(p) ^((L) ^(p,max) ⁾·L_(p,max).

In one example, a determination of CCE indexes for the M_(p,rem) ^((L)^(p,max1) ⁾ PDCCH candidates can be as in one of equations 2, 3A, or 3Bfor the determination of CCE indexes for the M_(p) ^((L) ^(p,max) ⁾PDCCH candidates by replacing L_(p,max) by L_(p,max1) and by replacingM_(p) ^((L) ^(p,max) ⁾ by M_(p,rem) ^((L) ^(p,max1) ⁾.

In one example, to avoid potential overlap for CCE indexes among theM_(p) ^((L) ^(p,max1) ⁾ PDCCH candidates, because CCE indexes for theM_(p) ^((L) ^(p,max1) ⁾−M_(p,rem) ^((L) ^(p,max1) ⁾ candidates aredetermined differently than CCE indexes for the M_(p,rem) ^((L)^(p,max1) ⁾ PDCCH candidates, a determination of CCE indexes for theM_(p,rem) ^((L) ^(p,max1) ⁾ PDCCH candidates can be, for example, as inone of equation 1 by considering all M_(p) ^((L) ^(p,max1) ⁾ PDCCHcandidates and selecting CCE indexes for the first M_(p,rem) ^((L)^(p,max1) ⁾ PDCCH candidates that do not overlap with CCE indexes forthe other M_(p) ^((L) ^(p,max1) ⁾−M_(p,rem) ^((L) ^(p,max1) ⁾ PDCCHcandidates.

When M_(p) ^((L) ^(p) ⁾·L_(p)>M_(p) ^((L) ^(p,max) ⁾·L_(p,max) also forat least one CCE aggregation level L_(p,max2) with L_(p,max2)<L_(p,max1)(and M_(p) ^((L) ^(p,max1) ⁾·L_(p,max1)>M_(p) ^((L) ^(p,max)⁾·L_(p,max)), such as L_(p,max1)=4 and L_(p,max2)=2, two cases can beconsidered. A first case considers that M_(p) ^((L) ^(p,max2)⁾·L_(p,max2)≤M_(p) ^((L) ^(p,max1) ⁾·L_(p,max1). In one example, CCEindexes for a number of M_(p,init) ^((L) ^(p,max2) ⁾=M_(p) ^((L)^(p,max1) ⁾·L_(p,max1)/L_(p,max2) PDCCH candidates can be determined,for example as in equation 4, while a number of M_(p,rem) ^((L)^(p,max2) ⁾=M_(p) ^((L) ^(p,max2) ⁾−M_(p,init) ^((L) ^(p,max2) ⁾ canagain be determined as in equation 4 after replacing L_(p,max) withL_(p,max1) and considering a set of CCEs corresponding to the M_(p,rem)^((L) ^(p,max1) ⁾ PDCCH candidates. In one example, a determination ofCCE indexes for PDCCH candidates with CCE aggregation level L_(p,max2)considers that a largest CCE aggregation level is L_(p,max1) (notL_(max,p)) and equation 4 can apply for all M_(p) ^((L) ^(p,max2) ⁾PDCCH candidates by replacing L_(p,max) with L_(p,max1).

This leads to a nested structure for a determination of CCE indexeswhere CCE indexes for PDCCH candidates with a largest CCE aggregationlevel in a control resource set p are first determined from a set of allCCE indexes in the control resource set p, CCE indexes for PDCCHcandidates with a second largest CCE aggregation level in the controlresource set p are determined either only from a set of CCE indexes forPDCCH candidates with the largest CCE aggregation level, when M_(p)^((L) ^(p,max1) ⁾·L_(p,max1)≤M_(p) ^((L) ^(p,max) ⁾·L_(p,max) or,otherwise, from both a set of CCE indexes for PDCCH candidates with thelargest CCE aggregation level for M_(p) ^((L) ^(p,max)⁾·L_(p,max)/L_(p,max1) PDCCH candidates and a set of all CCE indexes inthe control resource set p for M_(p) ^((L) ^(p,max1) ⁾−M_(p) ^((L)^(p,max) ⁾·L_(p,max)/L_(p,max1) (with possible adjustment to avoidoverlapping CCE indexes for PDCCH candidates with a same CCE aggregationlevel as it was previously described), CCE indexes for PDCCH candidateswith a third largest CCE aggregation level in the control resource set pare determined either only from a set of CCE indexes for PDCCHcandidates with the first largest CCE aggregation level, when M_(p)^((L) ^(p,max2) ⁾·L_(p,max2)≤M_(p) ^((L) ^(p,max1) ⁾·L_(p,max1) or,otherwise, from both a set of CCE indexes for PDCCH candidates with thesecond largest CCE aggregation level for M_(p) ^((L) ^(p,max1)⁾·L_(p,max1)/L_(p,max2) PDCCH candidates and a set of all CCE indexes inthe control resource set p for M_(p) ^((L) ^(p,max2) ⁾−M_(p) ^((L)^(p,max1) ⁾·L_(p,max1)/L_(p,max2), and so on.

In a second case, when M_(p) ^((L) ^(p,max2) ⁾·L_(p,max2)>M_(p) ^((L)^(p,max1) ⁾·L_(p,max1) (and M_(p) ^((L) ^(p,max1) ⁾·L_(p,max1)>M_(p)^((L) ^(p,max) ⁾·L_(p,max)), CCE indexes for a number of M_(p,init)^((L) ^(p,max2) ⁾=M_(p) ^((L) ^(p,max1) ⁾·L_(p,max1)/L_(p,max2) PDCCHcandidates with CCE aggregation level L_(p,max2) can be determined, forexample as in equation 4, by replacing L_(p,max) with L_(p,max1). CCEindexes for a number of remaining PDCCH candidates M_(p,rem) ^((L)^(p,max2) ⁾=M_(p) ^((L) ^(p,max2) ⁾−M_(p,init) ^((L) ^(p,max2) ⁾ can bedetermined as for the M_(p,rem) ^((L) ^(p,max1) ⁾ PDCCH candidates byusing L_(p,max2) instead of L_(p,max1).

A second realization considers that CCE indexes for PDCCH candidates aredetermined relative to CCE indexes for PDCCH candidates that require alargest number of CCEs.

A UE first determines a maximum for product values of M_(p) ^((L) ^(p)⁾·L_(p) for configured number of PDCCH candidates M_(p) ^((L) ^(p) ⁾with CCE aggregation level L_(p) in control resource set p.Corresponding M_(p) ^((L) ^(p) ⁾ and L_(p) values resulting to a maximumvalue for M_(p) ^((L) ^(p) ⁾·L_(p) are denoted as M_(p) ^((L) ^(p,nest)⁾ and L_(p,nest), respectively. Values ofM_(p) ^((L) ^(p,nest) ⁾ andL_(p,nest) can be different for different control resource sets. When asame maximum value of M_(p) ^((L) ^(p) ⁾·L_(p) exists for multiple L_(p)values, a selected L_(p) value can be any of the multiple L_(p) valuessuch as the smallest or the largest.

A UE then determines CCE indexes for M_(p) ^((L) ^(p,nest) ⁾ PDCCHcandidates, for example according to equation 1 or according to equation2. A resulting number of CCEs is N_(CCE,p,k,nest)=M_(p) ^((L) ^(p,nest)⁾·L_(p,nest). For example, with reference to equation 1, CCEs for PDCCHcandidate m, 0≤m≤M_(p) ^((L) ^(p,nest) ⁾−1, can be determined as givenin equation 5:

$\begin{matrix}{{{L_{p,{nest}} \cdot \{ {( {Y_{p,k} + \lfloor \frac{m \cdot N_{{CCE},p,k}}{L_{p,{nest}} \cdot M_{p}^{(L_{p,{nest}})}} \rfloor} ){mod}\lfloor {N_{{CCE},p,k}/L_{p,{nest}}} \rfloor} \}} + i},{i = 0},{{\ldots \mspace{14mu} L_{p,{nest}}} - 1}} & {{equation}\mspace{14mu} 5}\end{matrix}$

A UE subsequently determines CCEs for M_(p) ^((L) ^(p) ⁾ PDCCHcandidates, M_(p) ^((L) ^(p) ⁾, L_(p)≠L_(p,nest) by replacingN_(CCE,p,k) with N_(CCE,p,k,nest) and using, for example, equation 1, orusing equation 2. For example, with reference to equation 1, CCEs forM_(p) ^((L) ^(p) ⁾, L_(p)≠L_(p,nest), PDCCH candidates can be determinedas given in equation 6:

$\begin{matrix}{{{L_{p}\{ {( {Y_{p,k} + \lfloor \frac{m \cdot N_{{CCE},p,k,{nest}}}{L_{p} \cdot M_{p}^{(L_{p})}} \rfloor} ){mod}\lfloor {N_{{CCE},p,k,{nest}}/L_{p}} \rfloor} \}} + i},{i = 0},{{\ldots \mspace{14mu} L_{p}} - 1}} & {{equation}\mspace{14mu} 6}\end{matrix}$

FIG. 19 illustrates an example determination of CCEs 1900 for PDCCHcandidates based on a second realization according to embodiments of thepresent disclosure. An embodiment of the determination of CCEs 1900shown in FIG. 19 is for illustration only. One or more of the componentsillustrated in FIG. 19 can be implemented in specialized circuitryconfigured to perform the noted functions or one or more of thecomponents can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

As shown in FIG. 19, a UE is configured by a gNB a control resource setp, having a number of N_(CCE,p,k) CCEs and a number of M_(p) ^((L) ^(p)⁾ PDCCH candidates with CCE aggregation level L_(p) in the controlresource set p. It is also possible that values of M_(p) ^((L) ^(p) ⁾and L_(p) for predetermined values of N_(CCE,p,k) are determined in thespecifications of a system operation or are derived by the UE accordingto some specified formula. Based on the values of M_(p) ^((L) ^(p) ⁾ andL_(p), the UE determines a CCE aggregation level

$L_{p,{nest}} = {{\arg ( {\max\limits_{L_{p}}( {M_{p}^{(L_{p})} \cdot L_{p}} )} )}1910.}$

For each of the M_(p) ^((L) ^(p,nest) ⁾ PDCCH candidates, the UEdetermines respective CCE indexes according to a formula, such as forexample one of equation 1 or equation 2, considering the set of allN_(CCE,p,k) CCEs in control resource set p 1920.

For each of the M_(p) ^((L) ^(p) ⁾, L_(p)≠L_(p,nest), PDCCH candidates,the UE determines respective CCE indexes according to a formula, such asfor example one of equation 1 or equation 2, by considering the set ofCCE indexes for the M_(p) ^((L) ^(p,nest) ⁾ PDCCH candidates as a set ofavailable CCE indexes, that is, by replacing N_(CCE,p,k) withN_(CCE,p,k,nest)=M_(p) ^((L) ^(p,nest) ⁾·L_(p,nest) 1930.

FIG. 20 illustrates example CCE indexes 2000 of PDCCH candidates basedon the second realization according to embodiments of the presentdisclosure. An embodiment of the CCE indexes 2000 shown in FIG. 20 isfor illustration only. One or more of the components illustrated in FIG.20 can be implemented in specialized circuitry configured to perform thenoted functions or one or more of the components can be implemented byone or more processors executing instructions to perform the notedfunctions. Other embodiments are used without departing from the scopeof the present disclosure.

As shown in FIG. 20, a UE has M_(p))⁽¹⁾=2 PDCCH candidates for CCEaggregation level L_(p)=1 1910, M_(p) ⁽²⁾=6 PDCCH candidates for CCEaggregation level L_(p)=2 1920, M_(p) ⁽⁴⁾=4 PDCCH candidates for CCEaggregation level L_(p)=4 1930, and M_(p) ⁽⁸⁾=1 PDCCH candidates for CCEaggregation level L_(p)=8 1940. It is

$L_{p,{nest}} = {{\arg ( {\max\limits_{L_{p}}( {M_{p}^{(L_{p})} \cdot L_{p}} )} )} = 4.}$

The UE determines CCE indexes for the M_(p) ⁽⁴⁾=4 PDCCH candidates forCCE aggregation level L_(p)=4 considering all N_(CCE,p,k) CCEs 1950 incontrol resource set p in slot k. The CCE indexes form a set ofN_(CCE,p,k,nest) CCEs 1960. The UE determines CCE indexes for the M_(p)⁽¹⁾=2, M_(p) ⁽²⁾=6, and M_(p) ⁽⁸⁾=1 PDCCH candidates for CCE aggregationlevels L_(p)=1, L_(p)=2, and L_(p)=8, respectively, from CCE indexes inthe set of N_(CCE,p,k,nest) CCEs in control resource set p and slot k.

CCE indexes for PDCCH candidates can also be randomized, as describedfor the first realization, by having a determination for the parameterY_(p,k) in equation 1 depend on an index of a PDCCH candidate inaddition to a UE RNTI. Then, for example, CCE indexes can be determinedaccording equation 2, or according to equation 3A/3B (by replacingL_(p,max) with L_(p,nest) or L_(p) in general) and usingN_(CCE,p,k,nest) instead of N_(CCE,p,k) for CCE indexes corresponding toL_(p)≠L_(p,nest).

Further, an additional condition that can apply to both the firstrealization and the second realization of only to use different CCEindexes for PDCCH candidates with a same CCE aggregation level but, whenpossible, also use different CCE indexes for PDCCH candidates withdifferent CCE aggregation levels. This can be achieved by removing CCEindexes that have been allocated to PDCCH candidate from a set ofavailable CCE indexes and continuing in an iterative fashion. Forexample, starting from PDCCH candidates with a largest CCE aggregationlevel and a total set of available CCE indexes, {S_(CCE,p,k)}, a set of{S_(CCE,p,k,nest)} for PDCCH candidates of a CCE aggregation level canbe obtained. For example, the CCE aggregation level can be L_(p,max)according to the first realization or

$L_{p,{nest}} = {\arg ( {\max\limits_{L_{p}}( {M_{p}^{(L_{p})} \cdot L_{p}} )} )}$

according to the second realization.

From the set of {S_(CCE,p,k,nest)} CCE indexes, indexes of CCEs forPDCCH candidates with CCE aggregation level L_(p,max) when differentthan L_(p,nest), can be first determined and removed from{S_(CCE,p,k,nest)} to determine a second set of CCE indexes{S_(CCE,p,k,nest,1)}. From the set of {S_(CCE,p,k,nest,1)} CCEs, indexesof CCEs for PDCCH candidates with a second largest CCE aggregation levelL_(p,max1), when different than L_(p,nest), can be next determined andremoved from {S_(CCE,p,k,nest,1)} to determine a second set of CCEindexes {S_(CCE,p,k,nest,2)}, and so on. The process can continue untilCCE indexes for all PDCCH candidates of all CCE aggregation levels areallocated or until a set of available CCE indexes does not includeenough CCE indexes to allocate to PDCCH candidates of a CCE aggregationlevel without overlapping. In the latter case, the process can bereinitialized using the first set {S_(CCE,p,k,nest)} of CCE indexes.

A second embodiment of the present disclosure considers a mapping of aCCE to RE s and a mapping of PDCCH to CCEs considering a nested PDCCHsearch space.

When a UE is configured PDCCH candidates that map to a variable numberOFDM symbols, such as a first OFDM symbol or all OFDM symbols of a DLcontrol resource set in a slot, or to different OFDM symbols, such as afirst OFDM symbol or a second OFDM symbol, a number of CCEs that areavailable for mapping a PDCCH candidate can depend on a number ofrespective OFDM symbols used for the mapping. For example, a number ofCCEs available for mapping a PDCCH candidate over two OFDM symbols canbe two s larger than a number of CCEs available for mapping a PDCCHcandidate over one OFDM symbol.

This effectively creates multiple control resource subsets within onecontrol resource set where a control resource subset can be identifiedby a number or index of associated. OFDM symbols and all controlresource subsets spy a same BW as the control resource set. When allPDCCH candidates map to all OFDM symbols of a control resource set (thisis trivially the case when a control resource set includes only one OFDMsymbol), a nested search space can be obtained as described in theaforementioned embodiment of this disclosure.

FIG. 21 illustrates example control resource subsets 2100 in a controlresource set according to embodiments of the present disclosure. Anembodiment of the control resource subsets 2100 shown in FIG. 21 is forillustration only. One or more of the components illustrated in FIG. 21can be implemented in specialized circuitry configured to perform thenoted functions or one or more of the components can be implemented byone or more processors executing instructions to perform the notedfunctions. Other embodiments are used without departing from the scopeof the present disclosure.

As shown in FIG. 21, a UE is configured a set of PRBs 2110A and 2110Bfor a control resource set that spans two OFDM symbols. The set of PRBscan include PRBs that are either contiguous or non-contiguous infrequency. A first control resource subset includes all PRBs in thefirst OFDM symbol 2120, a second control resource subset includes allPRBs in the second OFDM symbol 2130, and a third control resource subsetis same as the control resource set and includes all PRBs in both thefirst and second OFDM symbols.

For the exemplary realization of control resource subsets in FIG. 21, anumber of CCEs in the first control resource subset is denoted asN_(CCE,p,k,1), a number of CCEs in the second control resource subset isdenoted as N_(CCE,p,k,2), and a number of CCEs in the control resourceset is denoted as N_(CCE,p,k). For example,N_(CCE,p,k,1)=N_(CCE,p,k,2)=N_(CCE,p,k)/2.

A nested search space structure when different PDCCH candidates map todifferent OFDM symbol indexes, including different numbers of OFDMsymbols, can be determined as follows. For a DL control resource set pthat includes N_(p) OFDM symbols, denote by L_(p,j) a CCE aggregationlevel L_(p) when CCEs are mapped over j OFDM symbols and by M_(p,j)^((L) ^(p) ⁾ a number of PDCCH candidates for CCE aggregation levelL_(p) that map to j OFDM symbols, 1≤j≤N_(p). For the purpose of defininga nested search space structure, an equal distribution of CCEs for aPDCCH candidate over j OFDM symbols and L_(p,j+1)=┌j·L_(p,j)/(j+1)┐,1≤j≤N_(p), are assumed. For example, when L_(p,1)=4, L_(p,2)=2,L_(p,3)=2, and L_(p,4)=1. Alternatively, only integer values ofj·L_(p,j)/(j+1), 1≤j≤N_(p), can be considered and then L_(p,3) is notdefined when L_(p)=2^(l), l is a non-negative integer.)

A UE first determines a maximum for product values of M_(p,j) ^((L) ^(p)⁾·L_(p) for 1≤j≤N_(p) and sets

$( {L_{p,j_{nest}},j_{nest}} ) = {{\arg ( {\max\limits_{L_{p},j}( {M_{p,j}^{(L_{p})} \cdot L_{p,j}} )} )}.}$

When multiple values for (L_(p,j) _(nest) ,j_(nest)) can exist, aselected value can be the one with the smallest L_(p,j) _(nest) or thesmallest j_(nest). Typically, it can be expected that j_(nest) is equalto the smallest value of 1≤j≤N_(p) with M_(p,j) ^((L) ^(p) ⁾>0, that is

$j_{nest} = {{\arg ( {\min\limits_{j}( {M_{p,j}^{(L_{p})} > 0} )} )}.}$

The UE then determines CCE indexes for M_(p,j) _(nest) ^((L) ^(p,nest) ⁾PDCCH candidates, for example according to equation 1 or equation 2.When there is a same number of CCEs per OFDM symbol, the CCE indexes forthe M_(p,j) _(nest) ^((L) ^(p,nest) ⁾ PDCCH candidates can be determinedrelative to CCE indexes in a first OFDM symbol of DL control resourceset p in slot k, N_(CCE,p,k,1), and CCEs in remaining of j_(nest) OFDMsymbols can have a same index as in the first OFDM symbol. Further, itis possible for CCE indexing to be per symbol instead of across allsymbols.

A resulting set of CCE indexes includes a number of N_(CCE,p,k,j)_(nest) =M_(p,j) _(nest) ^((L) ^(p,nest) ⁾·L_(p,j) _(nest) CCEs. Forexample, with reference to equation 1, a set of CCE indexes for PDCCHcandidate m, 0≤m≤M_(p) ^((L) ^(p,jnest) ⁾−1, in a first OFDM symbol ofDL control resource set p in slot k can be determined as in equation 7:

$\begin{matrix}{{{L_{p,j_{nest}}\{ {( {Y_{p,k} + \lfloor \frac{m \cdot N_{{CCE},p,k,1}}{L_{p,j_{nest}} \cdot M_{p}^{(L_{p,j_{nest}})}} \rfloor} ){mod}\lfloor {N_{{CCE},p,k,1}/L_{p,j_{nest}}} \rfloor} \}} + i},{i = 0},{{\ldots \mspace{14mu} L_{p,j_{nest}}} - 1.}} & {{equation}\mspace{14mu} 7}\end{matrix}$

A UE subsequently determines CCE indexes for M_(p,j) ^((L) ^(p) ⁾ PDCCHcandidates, by replacing the set of N_(CCE,p,k,1) CCE indexes in a firstOFDM symbol of DL control resource set p in slot k with the set ofN_(CCE,p,k,j) _(nest) =M_(p,j) _(nest) ^((L) ^(p,nest) ⁾·L_(p,j) _(nest)D CCE indexes and using equation 1 or equation 2. For example, withreference to equation 1, CCE indexes for M_(p,j) ^((L) ^(p) ⁾ PDCCHcandidates, L_(p,j)≠L_(p,j) _(nest) , can be determined as in equation8:

$\begin{matrix}{{{L_{p,j}\{ {( {Y_{p,k} + \lfloor \frac{m \cdot N_{{CCE},p,k,j_{nest}}}{L_{p,j} \cdot M_{p}^{(L_{p,j})}} \rfloor} ){mod}\lfloor {N_{{CCE},p,k,j_{nest}}/L_{p,j}} \rfloor} \}} + i},{i = 0},{{\ldots \mspace{14mu} L_{p,j}} - 1.}} & {{equation}\mspace{14mu} 8}\end{matrix}$

FIG. 22 illustrates example CCE indexes 2200 of PDCCH candidatesspanning one or two OFDM symbols in a nested structure according toembodiments of the present disclosure. An embodiment of the CCE indexes2200 shown in FIG. 22 is for illustration only. One or more of thecomponents illustrated in FIG. 22 can be implemented in specializedcircuitry configured to perform the noted functions or one or more ofthe components can be implemented by one or more processors executinginstructions to perform the noted functions. Other embodiments are usedwithout departing from the scope of the present disclosure.

As shown in FIG. 22, a UE is configured a DL control resource set pspanning two symbols. All PDCCH candidates for L_(p)=1 and L_(p)=2 spanone OFDM symbol and PDCCH candidates for L_(p)=4 and L_(p)=8 span bothOFDM symbols. The UE is configured the following PDCCH candidates:M_(p,1) ⁽¹⁾=4 on the first OFDM symbol and M_(p,1) ⁽¹⁾=2 on the secondOFDM symbol, M_(p,1) ⁽²⁾=6 on the first OFDM symbol and M_(p,1) ⁽²⁾=2 onthe second OFDM symbol, M_(p,2) ⁽⁴⁾=2, and M_(p,2) ⁽⁸⁾=1. Since

${( {L_{p,j_{nest}},j_{nest}} ) = {{\arg ( {\max\limits_{L_{p},j}( {M_{p,j}^{(L_{p})} \cdot L_{p,j}} )} )} = ( {2,1} )}},$

the UE determines a set of N_(CCE,p,k,1)=M_(p,1) ^((L) ^(p,1)⁾·L_(p,1)=12 CCEs in the first OFDM symbol 2210, for example accordingto equation 7. For example, the first, second, third, fourth, fifth, andsixth PDCCH candidates with CCE aggregation level L_(p)=2 in the firstOFDM symbol can use CCEs (1, 7), (2, 8), (3, 9), (4, 10), (5, 11) and(6, 12), respectively.

It is noted that actual indexes of CCEs 1 through 12 in FIG. 22 can bedifferent in the DL control resource set but they are the indexes in theset of N_(CCE,p,k,1)=12 CCEs. For remaining PDCCH candidates, CCEindexes can be determined from the set of N_(CCE,p,k,1)=12 using, forexample equation 8, and CCEs 1, 4, 7, and 10 can be used for respectiveM_(p,1) ⁽¹⁾=4 PDCCH candidates on the first OFDM symbol, CCEs 2 and 8can be used for respective M_(p,1) ⁽¹⁾=2 PDCCH candidates on the secondOFDM symbol, CCEs (2, 8) and (5, 11) can be used for respective M_(p,1)⁽²⁾=2 PDCCH candidates on the second OFDM symbol, CCEs (3, 9) and (6,12) on both OFDM symbols can be used for respective M_(p,2) ⁽⁴⁾=2 PDCCHcandidates, and CCEs (1, 7), (3, 9), (4, 10) and (6, 12) on both OFDMsymbols can be used for the M_(p,2) ⁽⁸⁾=1 PDCCH candidate.

A nested PDCCH search space structure can be primarily applicable todistributed PDCCH transmissions where blocks of one or more REGs for aCCE can be distributed in frequency and PDCCH candidates can share a setof CCE indexes. For localized PDCCH transmission, where REGs (and CCEs)for a PDCCH candidate are contiguous in frequency, a nested search spacestructure is more difficult to achieve when CCEs for PDCCH candidatesare distributed in frequency in order to increase the likelihood forselecting CCEs where a UE experiences favorable channel conditions. Forexample, for a DL control resource set spanning one OFDM symbol and forM_(p) ⁽¹⁾=6 PDCCH candidates with CCE aggregation level L_(p)=1 and forM_(p) ⁽²⁾=4 PDCCH candidates with CCE aggregation level L_(p)=2, eventhough all M_(p) ^((L) ^(p) ⁾·L_(p)=6·1=6 CCE indexes for the M_(p) ⁽¹⁾PDCCH candidates can be a subset of the M_(p) ^((L) ^(p) ⁾·L_(p)=4·2=8CCE indexes for the M_(p) ⁽²⁾PDCCH candidates, this would require thatthe CCEs for 2 PDCCH candidates with L_(p)=1 are contiguous to CCEs of 2other PDCCH candidates with L_(p)=¹ and this reduces the likelihood ofselecting a CCE for PDCCH transmission where a UE experiences favorablechannel conditions.

The limitation of a nested search space design for localized PDCCHtransmissions can be addressed by limiting a use of a nested searchspace only to distributed PDCCH transmissions and using an unconstrainedsearch space design, for example as in equation 1, for localized PDCCHtransmissions. Nevertheless, in order for a UE to benefit also a reducednumber of channel estimates the UE need to compute per slot, it can bepossible to apply a nested search space design also for localized PDCCHtransmissions.

In a first approach, for localized PDCCH transmissions, a nested searchspace design can be have a nested allocation of CCEs for PDCCHcandidates where CCE indexes for CCE aggregation levels with thesmallest number of candidates overlap with CCE indexes for CCEaggregation levels with the second smallest number of candidates, CCEindexes for CCE aggregation levels with the second smallest number ofcandidates overlap with CCE indexes for CCE aggregation levels with thethird smallest number of candidates, and so on.

In a second approach, CCE indexes can determined as for a distributedtransmission and it is possible that for some PDCCH candidates to havecontiguous CCEs in the frequency domain.

When a DL control resource set includes multiple OFDM symbols, it can bepossible to restrict PDCCH candidates for the larger CCE aggregationlevels, such as 4 CCEs or 8 CCEs, to be over the multiple OFDM symbolsin order to restrict a frequency span for the PDCCH candidates andreduce a number of RBs where a UE needs to obtain a channel estimate.PDCCH candidates for the smaller CCE aggregation levels, such as oneCCE, can have respective REGs either only on one OFDM symbol or onmultiple OFDM symbols.

Further, it can be possible to configure a transmission of a localizedPDCCH candidate to span all OFDM symbols, regardless of the CCEaggregation level, while a transmission of a distributed PDCCH candidatecan span either one OFDM (particularly for the smaller CCE aggregationlevels) or all OFDM symbols of a DL control resource set (particularlyfor the larger CCE aggregation levels).

FIG. 23 illustrates an example nested allocation of CCE indexes 2300 toPDCCH candidates based on an ascending order of PDCCH candidatesaccording to embodiments of the present disclosure. An embodiment of thenested allocation of CCE indexes 2300 shown in FIG. 23 is forillustration only. One or more of the components illustrated in FIG. 23can be implemented in specialized circuitry configured to perform thenoted functions or one or more of the components can be implemented byone or more processors executing instructions to perform the notedfunctions. Other embodiments are used without departing from the scopeof the present disclosure.

As shown in FIG. 23, a UE is configured a DL control resource set pspanning one symbol. There are M_(p,1) ⁽¹⁾=6 PDCCH candidates with CCEaggregation level L_(p)=1, M_(p,1) ⁽²⁾=4 PDCCH candidates with CCEaggregation level L_(p)=2, M_(p,1) ⁽⁴⁾=2 PDCCH candidates with CCEaggregation level L_(p)=4, and M_(p,1) ⁽⁸⁾=1 PDCCH candidates with CCEaggregation level L_(p)=8. A UE can first determine CCE indexes for aCCE aggregation level with a largest number of PDCCH candidates (M_(p,1)⁽¹⁾=6) according, for example, to equation 1 2310. The UE uses the setof CCEs for the M_(p,1) ⁽¹⁾=6 PDCCH candidates to determine CCE indexesfor the M_(p,1) ⁽²⁾=4 PDCCH candidates using, for example, equation 1with L_(p)=1 to obtain one CCE index for each of the M_(p,1) ⁽²⁾=4 PDCCHcandidates and determining the other CCE index for each of the M_(p,1)⁽²⁾==4 PDCCH candidates as a respective next (or previous) CCE index2320.

The UE uses the set of CCEs for the M_(p,1) ⁽¹⁾=6 PDCCH candidates todetermine CCE indexes for the M_(p,1) ⁽⁴⁾=2 PDCCH candidates using, forexample, equation 1 with L_(p)=1 to obtain one CCE index for the M_(p,1)⁽⁴⁾=2 PDCCH candidates and determining the other three CCE indexes foreach of the M_(p,1) ⁽⁴⁾=2 PDCCH candidates as a respective previousthree (or next three) CCE indexes 2330 and 2335. The UE uses the set ofCCEs for the M_(p,1) ⁽¹⁾=6 PDCCH candidates to determine CCE indexes forthe M_(p,1) ⁽⁸⁾=1 PDCCH candidate using, for example, equation 1 withL_(p)=1 to obtain one CCE index for the M_(p,1) ⁽⁸⁾=1 PDCCH candidateand determine the other seven CCE indexes as a next seven (or previousseven) CCE indexes 2340. When there is not a sufficient number of next(or previous) CCE indexes, previous (or next, respectively) CCE indexescan be used.

FIG. 24 illustrates an example nested allocation of CCE indexes 2400 toPDCCH candidates based on a restriction in CCE indexes for a number ofPDCCH candidates according to embodiments of the present disclosure. Anembodiment of the nested allocation of CCE indexes 2400 shown in FIG. 24is for illustration only. One or more of the components illustrated inFIG. 24 can be implemented in specialized circuitry configured toperform the noted functions or one or more of the components can beimplemented by one or more processors executing instructions to performthe noted functions. Other embodiments are used without departing fromthe scope of the present disclosure.

As shown in FIG. 24, a UE is configured a DL control resource set pspanning one symbol. There are M_(p,1) ⁽¹⁾=6 PDCCH candidates with CCEaggregation level L_(p)=1, M_(p,1) ⁽²⁾=4 PDCCH candidates with CCEaggregation level L_(p)=2, M_(p,1) ⁽⁴⁾=2 PDCCH candidates with CCEaggregation level L_(p)=4, and M_(p,1) ⁽⁸⁾=1 PDCCH candidate with CCEaggregation level L_(p)=8. A UE can first determine CCE indexes for aCCE aggregation level determined as

${\arg ( {\max\limits_{L_{p}}( {M_{p}^{(L_{p})} \cdot L_{p}} )} )} = 2$

according, for example, to equation 1 2410, 2415. The UE uses the set ofCCEs for the M_(p,1) ⁽²⁾=4 PDCCH candidates to determine CCE indexes forthe M_(p,1) ⁽¹⁾=6 PDCCH candidates using, for example, equation 1 withL_(p)=1 to obtain one CCE indexes for each of the M_(p,1) ⁽¹⁾M=6 PDCCHcandidates 2420.

The UE uses the set of CCEs for the M_(p,1) ⁽²⁾=4 PDCCH candidates todetermine CCE indexes for the M_(p,1) ⁽⁴⁾=2 PDCCH candidates using, forexample, equation 1 with L_(p)=2 to obtain two CCE indexes for theM_(p,1) ⁽⁴⁾=2 PDCCH candidates and determining the other two CCE indexesfor each of the M_(p,1) ⁽⁴⁾=2 PDCCH candidates as a respective previoustwo (or next two) CCE indexes 2430. The UE uses the set of CCEs for theM_(p,1) ⁽²⁾2=4 PDCCH candidates to determine CCE indexes for the M_(p,1)⁽⁸⁾=1 PDCCH candidate using, for example, equation 1 with L_(p)=2 toobtain two CCE indexes for the M_(p,1) ⁽⁸⁾=1 PDCCH candidate anddetermine the other six CCE indexes as a next six (or previous six) CCEindexes 2440. When there is not a sufficient number of next (orprevious) CCE indexes, previous (or next, respectively) CCE indexes canbe used.

An UL DMRS or SRS transmission can be based on a transmission of aZadoff-Chu (ZC) sequence, a CAZAC sequence, or a pseudo-noise (PN)sequence. For example, for a UL system BW of N_(RB) ^(max,UL) RBs, a ZCsequence r_(u,v) ^((α))(n) can be defined by a cyclic shift (CS) α of abase sequence r _(u,v)(n) according to r_(u,v) ^((α))(n)=e^(jαn) r_(u,v)(n), 0≤n<M_(sc) ^(RS), where M_(sc) ^(RS)=mN_(sc) ^(RB) is asequence length, 1≤m≤N_(RB) ^(max,UL), and r _(u,v)(n)=x_(q)(n modN_(ZC) ^(RS)) where the q^(th) root ZC sequence is defined by

${{x_{q}(m)} = {\exp ( \frac{{- j}\; \pi \; {{qm}( {m + 1} )}}{N_{ZC}^{RS}} )}},$

0≤m≤N_(ZC) ^(RS)−1 with q given by q=└q+½┘+v·(−1)^(└2q┘) and q given byq=N_(ZC) ^(RS)·(u+1)/31. A length N_(ZC) ^(RS) of a ZC sequence is givenby a largest prime number such that N_(ZC) ^(RS)<M_(sc) ^(RS).

Multiple RS sequences can be defined from a single base sequence usingdifferent values of α. UL DMRS or SRS transmissions can have a combspectrum where non-consecutive SCs are used for transmission in a slotsymbol. An SRS transmission is identified by a set of respectiveparameters such as a transmission comb, a cyclic shift, a BW, a startingposition in a system BW, a number of transmitted antenna ports, a timingoffset for a first transmission, or a number of transmission symbols.

CSI-RS can be transmitted on a number of antenna ports, such as one,two, four, eight, twelve, or sixteen antenna ports. For CSI-RS usingmore than eight antenna ports, N_(res) ^(CSI)>1 CSI-RS configurations ina same slot are aggregated to obtain a total of N_(res) ^(CSI)N_(ports)^(CSI) antenna ports. Each CSI-RS configuration in such an aggregationcorresponds to N_(ports) ^(CSI)∈{4,8} antenna ports. A mapping of aCSI-RS to REs in a slot is described in LTE specification.

Multiple CSI-RS configurations can be used in a cell. A UE can beconfigured with multiple sets of CSI-RS including up to threeconfigurations for NZP CSI-RS the UE can use for CSI reporting and zeroor more configurations for ZP CSI-RS. The NZP CSI-RS configurations areprovided by higher layers. The ZP CSI-RS configurations in a slot can begiven by a bitmap derived.

A UE can be configured with one or more CSI-RS resource configuration(s)that can include the following parameters. In one example, one or moreCSI-RS resource configuration(s) include CSI-RS resource configurationidentity. In another example, one or more CSI-RS resourceconfiguration(s) include a number of CSI-RS ports. For example,allowable values and antenna port mapping can be as described in the LTEspecifications. In yet another example, one or more CSI-RS resourceconfiguration(s) include CSI-RS configuration as described in the LTEspecifications. In yet another example, one or more CSI-RS resourceconfiguration(s) include UE assumption on reference PDSCH transmittedpower for CSI feedback P_(c) for each CSI process. When CSI slot setsC_(CSI,0) and C_(CSI,1) are configured by higher layers for a CSIprocess, P_(c) is configured for each CSI slot set of the CSI process.In yet another example, one or more CSI-RS resource configuration(s)include pseudo-random sequence generator parameter, n_(ID). In yetanother example, one or more CSI-RS resource configuration(s) includeCDM type parameter, if UE is configured with higher layer parametereMIMO-Type and eMIMO-Type is set to “CLASS A” for a CSI process asdescribed in the LTE specifications.

A UE can be configured with one or more CSI resource configuration(s)for interference measurement (CSI-IM). A UE is typically not expected toreceive a CSI-IM resource configuration that is not completelyoverlapping with one of the ZP CSI-RS resource configurations.

Based on a computation of a CQI, a UE can derive a CQI index between 1and 15 corresponding to a modulation scheme and transport block sizethat the UE can receive with BLER not exceeding a predetermined value,such as 10%. If this is not possible, the UE reports a CQI index of 0.An interpretation of CQI indices is given in Table 1 and differentmapping tables can also exist.

TABLE 1 4-bit CQI Table for Conventional UEs CQI Bits CQI indexModulation code rate × 1024 efficiency 0000 0 out of range 0001 1 QPSK78 0.1523 0010 2 QPSK 120 0.2344 0011 3 QPSK 193 0.3770 0100 4 QPSK 3080.6016 0101 5 QPSK 449 0.8770 0110 6 QPSK 602 1.1758 0111 7 16QAM 3781.4766 1000 8 16QAM 490 1.9141 1001 9 16QAM 616 2.4063 1010 10 64QAM 4662.7305 1011 11 64QAM 567 3.3223 1100 12 64QAM 666 3.9023 1101 13 64QAM772 4.5234 1110 14 64QAM 873 5.1152 1111 15 64QAM 948 5.5547

A network can support UEs with different transmission or reception BWcapabilities. For example, a network can have an available a system DLBW or UL BW of 200 MHz while a UE of a certain category can be able toor be configured to receive or transmit only in a smaller BW than thesystem DL BW or UL BW, such as in 20 MHz. Despite a transmission BW orreception BW of a UE being respectively smaller than a DL BW or an UL BWof a system, a gNB can schedule receptions or transmissions from the UEin any part of a respective system BW.

A gNB can configure a UE narrowbands (NBs) of a DL system BW or an ULsystem BW, where a BW of each NB does not exceed the UE capability for areception BW or transmission BW, and schedule transmissions to the UE ortransmissions from the UE in a respective NB. NBs can have a same sizeor different sizes. For example, all NBs can have a same size except fora last NB that can have same or smaller size than other NBs.

The term narrowband is used as reference and any other term, such assub-band or BW part, can be used instead to denote a partitioning unitof a system BW into smaller BWs. Further, the NBs can be non-overlappingor can partially overlap.

DL DCI formats or UL DCI formats scheduling, respectively, transmissionsto or from a UE can include a first field indicating an NB and a secondfield indicating resources within the NB. It is also possible that bothan NB and an allocation of PRBs within the NB are indicated by a singlefield. In order for a gNB to select an NB among a set of NBs forscheduling receptions or transmissions from a UE while improving asystem spectral efficiency, the gNB needs to be provided with CSI fromthe UE for NBs from the set of NBs. A UE can provide a CSI report to agNB for an NB from a set of NBs either by transmitting a CSI report forthe NB or by transmitting SRS in the NB to the gNB. A UE can transmitCSI reports in a PUCCH or a PUSCH in resources configured by a gNB byhigher layer signaling or by physical layer (L1) signaling.

A UE can obtain a CSI report for an NB by measuring a CSI-RS transmittedin the NB. This requires that a UE retunes the UE's radio frequency (RF)receiver to an NB in order to receive a CSI-RS. As an NB for CSI-RSreception can be different than an NB a UE is configured to receivePDCCHs, this requires two retuning operations; one from an NB configuredfor PDCCH receptions to an NB of a CSI-RS transmission and another fromthe NB of CSI-RS transmission to the NB of PDCCH transmissions. As an RFretuning operation for a UE receiver requires a time period where the UEcannot receive signaling, it can limit scheduling opportunities of a UEand limit achievable data rates for the UE. It is therefore beneficialto reduce a time where a UE cannot receive DL control channels due to aretuning operation.

For an SRS transmission from a UE over a BW that is larger than amaximum SRS transmission BW the UE can support, the UE can transmit SRSin different NBs of the BW during respective different time instances.Further, a UE capability for simultaneously receiving from a number ofantennas can be larger than a UE capability for simultaneouslytransmitting from a number of antennas. For a TDD system, due to areciprocal DL BW and UL BW, SRS transmissions from a UE can provide CSIfor DL transmissions to the UE and it is therefore beneficial to enableSRS transmission from all UEs antennas.

Therefore, there is a need for a gNB to trigger CSI-RS transmissions atdifferent time instances in different narrowbands.

There is another need for a UE to measure a CSI-RS at different timeinstances in different narrowbands.

There is another need to for a UE to provide CSI reports for differentnarrowbands.

There is another need to configure a UE with resources for transmissionof CSI reports.

There is another need to reduce an impact of RF retuning on a UEscheduling.

Finally, there is another need to enable a UE to transmit SRS indifferent narrowbands.

In one embodiment, designs for triggering CSI-RS transmissions onmultiple NBs are considered. CSI-RS transmissions in NBs can be precodedor non-precoded. In the former case, a precoding can also be configuredto a UE and can be same for all NBs (single configuration for all NBs)or can be different for different NBs (separate configuration per NB).CSI-RS transmissions can include zero-power CSI-RS and non-zero-powerCSI-RS.

In order for a UE to receive CSI-RS in NBs from a configured set of NBs,the UE needs to retune the UE's RF receiver components to each NB fromthe set of NBs. Depending on whether the NBs in the set of NBs are in asame frequency band or in different frequency bands and depending on aslot duration and on a UE retuning capability, an associated RF retuningdelay can vary from one or few symbols of a slot to one or more slots.While the UE is retuning the UE's receiver RF, the UE cannot receiveother signaling from a gNB. Therefore, a CSI-RS transmission in a slotneeds to account for a retuning delay while enabling a UE to bescheduled DL or UL transmissions through PDCCH receptions in an NB wherethe UE is configured to receive PDCCH.

When a retuning delay is smaller than a time interval between a lastslot symbol where a UE is configured to receive PDCCHs in a first NB anda first slot symbol of a CSI-RS transmission in a second NB, the UE canreceive CSI-RS in the second NB after receiving PDCCHs in the first NBwhen the UE does not receive other signaling, such as a PDSCH in thefirst NB and in the first slot or the second slot.

When a retuning delay is smaller than a time interval between a lastslot symbol for receiving CSI-RS in the second NB and a first slotsymbol for receiving PDCCHs in the first NB, the UE can retune to thefirst NB to receive PDCCHs after receiving CSI-RS in the second NB. Whenthe UE detects a PDCCH that schedules the UE to receive a PDSCH in afirst NB and the UE is also configured to receive CSI-RS in a second NBand a time between the end of the PDSCH reception and the start of theCSI-RS reception is smaller than a retuning delay from the first NB tothe second NB, the UE can drop reception of the CSI-RS.

For a TDD system and a UE with a single duplexer, when the UE isconfigured to transmit a random access channel, or a PUSCH, or a PUCCHsuch as one conveying HARQ-ACK in a first NB and the UE is alsoconfigured to receive CSI-RS in a second NB and the retuning delay islarger than a time between an end of UL signaling and the start ofCSI-RS reception, the UE can drop reception of the CSI-RS. For a TDDsystem and a UE with a single duplexer, when the UE is configured totransmit SRS in an NB and the UE is also configured to receive CSI-RS ina different NB and the retuning delay is such that the UE cannottransmit the SRS or receive the CSI-RS, the UE can prioritize receptionof the CSI-RS and drop transmission of SRS. The UE can report a lastvalid CSI measurement for an NB that the UE dropped a CSI-RS reception.

In one example, CSI-RS transmission in a set of one or more NBs can besemi-persistent or periodic. A UE is configured by higher layers a setof NBs and parameters for CSI-RS transmission in each NB from the setNBs. Each NB in the set of NBs has a respective index that isdetermined, for example, according to an ascending order in a system BW.CSI-RS transmissions can also occur according to an ascending order ofNB indexes except possibly for a CSI-RS transmission in an NB where a UEis configured to receive PDCCHs, as is further subsequently discussed,where a CSI-RS transmission can occur first. The CSI-RS transmissionparameters can be same for all NBs and can be jointly configured for allNBs, except possibly for a location of slot symbols for CSI-RStransmissions as it is further discussed in the following, or can beseparately configured for each NB.

CSI-RS transmission parameters can include one or more of a CSI-RSresource configuration identity, a number of CSI-RS ports, a CSI-RSconfiguration, a reference P_(c) power for each CSI process, apseudo-random sequence generator parameter, n_(ID), and a CDM typeparameter as they were previously described. CSI-RS transmissionparameters can also include a reference slot and a periodicity forCSI-RS transmission in each NB, a number of symbols for CSI-RStransmission in a slot, or a CSI process identity.

FIG. 25 illustrates example CSI-RS transmissions 2500 in a number of NBswhere a UE retunes to an NB that the UE is configured for PDCCHreceptions after receiving a CSI-RS transmission according toembodiments of the present disclosure. An embodiment of the CSI-RStransmissions 2500 shown in FIG. 25 is for illustration only. One ormore of the components illustrated in FIG. 25 can be implemented inspecialized circuitry configured to perform the noted functions or oneor more of the components can be implemented by one or more processorsexecuting instructions to perform the noted functions. Other embodimentsare used without departing from the scope of the present disclosure.

As shown in FIG. 25, a UE is configured a set of NBs that includes fourNBs and resources in a first NB from the four NBs for PDCCH receptions.In a first slot, the UE receives PDCCHs in the first NB 2510 and CSI-RStransmissions in the first NB 2515. In a second slot, the UE receivesPDCCHs in the first NB 2520, retunes to a second NB to receive CSI-RStransmissions 2525, and retunes back to the first NB to receive PDCCHsin a third slot. In the third slot, the UE receives PDCCHs in the firstNB 2530, retunes to a third NB to receive CSI-RS transmissions 2535, andretunes back to the first NB to receive PDCCHs in a fourth slot.

In the fourth slot, the UE receives PDCCHs in the first NB 2540, retunesto a fourth NB to receive CSI-RS transmissions 2545, and retunes back tothe first NB to receive PDCCHs in a fifth slot. The retuning in a slotto a NB other than the current active NB where the UE receives PDCCHscan be conditioned on the UE not having a scheduled reception in thecurrent active NB in the slot. Although FIG. 25 considers that a CSI-RStransmission for the UE occurs with a same periodicity in each NB, adifferent periodicity is also possible where, for example, a periodicityof CSI-RS transmission in the first NR is smaller than in other NBs fromthe set of NBs.

Instead of a UE retuning to an NB the UE is configured for PDCCHreceptions, the UE can be configured to retune to an NB of a next CSI-RStransmission. For example, when a slot includes fourteen symbols, aretuning delay is one symbol and a last symbol for PDCCH receptions in aslot is a third symbol, the UE can receive CSI-RS in all NBs prior toretuning to the NB where the UE in configured to receive PDCCHs.

Whether or not the UE retunes to a new NB to receive CSI-RStransmissions or to a configured NB to receive PDCCHs can depend on atime the UE requires to retune between NBs (retuning delay), on a numberof NBs in a set of NBs with CSI-RS transmissions, or on a slot duration,or on a maximum duration for PDCCH transmissions.

An intermediate behavior relative to the ones in FIG. 25 and FIG. 26 isalso possible when a UE retuning time, a slot duration, and a maximumduration for transmission of DL control channels are such that the UEcan receive CSI-RS transmissions in a sub-set of the set of NBs prior toretuning to an NB configured for PDCCH receptions and then retune to adifferent sub-set of the set of NBs for respective receptions of CSI-RStransmissions.

FIG. 26 illustrates example CSI-RS transmissions 2600 in a number of NBswhere a UE retunes to each NB configured for reception of a CSI-RStransmission prior to retuning to an NB configured for PDCCH receptionsaccording to embodiments of the present disclosure. An embodiment of theCSI-RS transmissions 2600 shown in FIG. 26 is for illustration only. Oneor more of the components illustrated in FIG. 26 can be implemented inspecialized circuitry configured to perform the noted functions or oneor more of the components can be implemented by one or more processorsexecuting instructions to perform the noted functions. Other embodimentsare used without departing from the scope of the present disclosure.

As shown in FIG. 26, a UE is configured a set of NBs that includes threeNBs and resources in a first NB from the three NBs for PDCCH receptions.In a first slot, the UE receives PDCCHs 2610 and first CSI-RStransmissions 2620 in the first NB. The UE subsequently retunes to asecond NB to receive CSI-RS transmissions 2630 and then to a third NB toreceive third CSI-RS transmissions 2640. After receiving the CSI-RStransmissions in the three NBs, the UE retunes to the first NB toreceive PDCCHs in a second slot 2650.

In another example, CSI-RS transmission in NBs from a set of NBs can beaperiodic and triggered by a DCI format conveyed by a PDCCH. The DCIformat can be a DL DCI format scheduling a PDSCH transmission to a UE orcan be a separate DCI format with contents for one or more UEs.

When a DCI format triggering CSI-RS transmissions in one or more NBsfrom a set of NBs is a DL DCI format scheduling a PDSCH transmission toa UE in one or more slots, the DL DCI format can include a fieldindicating one or more NBs from the set of NBs for CSI-RS transmission.As the DL DCI format schedules a PDSCH transmission to the UE, when anNB of the PDSCH transmission is also an NB with triggered CSI-RStransmission then, in order to be able to receive the PDSCH, a firstCSI-RS transmission can occur in the NB where the UE is configured toreceive PDCCHs and subsequent CSI-RS transmissions are in remaining NBsaccording to an ascending (or descending) order of an NB index.

When an NB where a UE is configured to receive PDCCHs is not an NB withtriggered CSI-RS transmission, the UE can receive the PDSCH in the oneor more slots and subsequently, after the one or more slots, retune toNBs with triggered CSI-RS transmission. It is also possible that CSI-RStransmissions in NBs are according to an ascending NB index including,when a CSI-RS transmission is triggered, an NB of a scheduled DL datachannel transmission. Depending on a retuning delay, the UE can alsoreceive PDCCHs in an NB in a next slot prior to retuning and, when theUE detects another DL DCI format in the next slot scheduling PDSCHtransmission to the UE in a first NB in one or more next slots, the UEcan ignore triggered CSI-RS transmissions in NBs other than the first NBin the one or more next slots.

A field in a DL DCI format triggering CSI-RS transmission in one or moreNBs from a set of NBs that a UE is configured can include an indicationof the NBs. For example, a field with two binary elements (bits) canindicate no CSI-RS transmissions using a “00” value, and indicate CSI-RStransmission in a first, second, or third configured sub-sets of NBsfrom the set of NBs using a “01,” a “10” and a “11” value, respectively.Parameters for CSI-RS transmission in each NB can be same or different.As it was previously described, it is also possible to use a separatefield for indicating a NB for a CSI-RS reception and use the fieldtriggering the CSI-RS reception to indicate a CSI-RS configuration.

For example, a CSI-RS resource configuration identity, a number ofCSI-RS ports, a CSI-RS configuration, a reference P_(c) power for eachCSI process, a pseudo-random sequence generator parameter, n_(ID), a CDMtype parameter, a number of symbols in a slot, or a CSI process identitycan be same for all NBs. A location of slot symbols for CSI-RStransmission in each NB can be same or different. For example, whenCSI-RS transmission is in different slots in respective different NBs,respective slot symbols can be same. For example, when CSI-RStransmission in at least some NBs are in a same slot, respective slotsymbols are different and a respective offset in number of symbols forsuccessive CSI-RS transmissions can be determined from a retuning delayfor UEs with associated triggered CSI-RS transmissions or can besignaled by a gNB either by UE-common higher layer signaling, such assystem information, or by UE-specific higher layer signaling.

A DL DCI format scheduling a DL data channel transmission to a UE andtriggering receptions by the UE of respective CSI-RS transmissions inone or more NBs from a set of NBs can also trigger a PUCCH transmissionfrom the UE conveying a CSI report for the one or more NBs. A resourcefor the PUCCH transmission can be explicitly indicated in the DL DCIformat or can be configured to the UE by higher layer signaling.

In a first example, the DL DCI format can include a PUCCH resourceallocation field for CSI reporting. A UE can be configured by higherlayers four PUCCH resources and a PUCCH resource allocation field forCSI reporting can include two bits to indicate one of the fourconfigured resources.

In a second example, the DL DCI format can include a PUCCH resourceallocation field for HARQ-ACK reporting associated with a receptionoutcome by the UE for the DL data channel. For example, a UE can beconfigured by higher layers four PUCCH resources and a PUCCH resourceallocation field for HARQ-ACK reporting can include two bits to indicateone of the four configured resources. Then, a PUCCH resource for CSIreporting can be derived from the PUCCH resource for HARQ-ACK reporting.The UE can also be configured by higher layers four PUCCH resources forCSI reporting and when, for example, a third PUCCH resource is indicatedfor HARQ-ACK reporting, the UE also uses a third PUCCH resource for CSIreporting. Therefore, PUCCH resources for HARQ-ACK reporting and for CSIreporting are different but are jointly indicated.

A same approach can apply for transmission timing of a HARQ-ACK reportand of a CSI report. For example, to avoid simultaneous transmissionsfrom a UE of a first PUCCH conveying a HARQ-ACK report and of a secondPUCCH conveying a CSI report, the UE can transmit the CSI report in anext slot, or in a predetermined slot, after the slot where the UEtransmits the CSI report. A UE can also be configured to transmitsuccessive PUCCHs in respective different symbols of a same slot. The DLDCI format can also include a TPC command for the UE to adjust a PUCCHtransmission power for HARQ-ACK reporting, and assuming a sameclosed-loop power control process for PUCCH transmissions, the UEapplies the TPC command also for adjusting a PUCCH transmission powerfor CSI reporting.

When a DCI format triggering CSI-RS transmissions in NBs from a set ofNBs for a UE is not a DL DCI format, the DCI format can have a same sizeas a DL DCI format that the UE decodes, or as a size of a DCI formatthat the UE decodes for other purposes such as for obtaining TPCcommands. A CRC of the DCI format can be scrambled with an RNTI specificto triggering of CSI-RS transmissions such as a CSI-RS-RNTI. A DCIformat with a CSI-RS-RNTI is referred to for brevity as DCI format T.Using a DCI format T, a gNB can trigger CSI-RS transmissions indifferent NBs from a configured set of NBs, and possibly also indifferent cells, for each UE from a group of UEs configured with a sameCSI-RS-RNTI.

A UE can be configured a location in DCI format T where the UE canobtain a CSI-RS trigger field indicating CSI-RS transmissions in asubset of NBs from the configured set of NBs through a parameterIndex-CSI-RS. For example, as described for a DL DCI format, a CSI-RStrigger field can have two bits or can have a larger number of bits thanin a DL DCI format for increased granularity where a value of “00” canindicate no CSI-RS transmissions and remaining values can indicateCSI-RS transmissions in respective configured subsets of NBs (includingall NBs in the set of NBs).

For example, an increased granularity can be useful when there is alarge number of NBs in the set of NBs or when a UE can be triggeredCSI-RS transmissions both in multiple NBs and in multiple cells or inmultiple sets of slots. Alternatively, DCI format T can include separateCSI-RS trigger fields for sets of NBs on respective different cells fora same UE. It is also possible that, when a CSI-RS trigger fieldtriggers CSI-RS transmissions, it does so for all NBs in the set of NBs.Then, the CSI-RS trigger field can include a single bit for each UE percell where a value of “0” indicates no CSI-RS triggering and a value of“1” indicates CSI-RS triggering in all NBs in the set of NBs.

A DCI format T can also include a field indicating a PUCCH resource fora transmission of a PUCCH conveying a CSI report from a UE in responseto measurements associated with triggered CSI-RS transmissions in NBsfrom a configured set of NBs and a field conveying a TPC command for thePUCCH transmission. The PUCCH resource field can be an index to a PUCCHresource from a configured set of PUCCH resources.

For example, when a PUCCH resource field includes two bits, the PUCCHresource field can indicate one out of four configured PUCCH resources.A location of the PUCCH resource field or a location of a TPC commandfield can be linked to a configured location of a CSI-RS trigger field,for example, the PUCCH resource field can be in a next location and theTPC command field can be in a location after the next location (or thereverse or in a previous location).

DCI format T can also indicate a single PUCCH resource for atransmission of a PUCCH that conveys a CSI report associated with afirst location where a CSI-RS trigger field in DCI format T does nothave a “00” value and PUCCH resources for PUCCH transmissions conveyingother CSI reports can be determined relative to the indicated PUCCHresource.

For example, a UE with a first location in DCI format T for a CSI-RStransmission trigger field with value different than “00” can use theindicated, first, PUCCH resource to transmit a PUCCH that conveys a CSIreport, a UE with a second location in DCI format T for a CSI-RStransmission trigger field with value different than “00” can use asecond PUCCH resource after the first PUCCH resource, a UE with a thirdlocation in DCI format T for a CSI-RS transmission trigger field withvalue different than “00” can use a third PUCCH resource after thesecond PUCCH resource, and so on.

Therefore, when PUCCH resource n_(PUCCH) is indicated in DCI format T, aUE with n_(CSI-RS)-th CSI-RS transmission trigger value that isdifferent than “00” can use PUCCH resource n_(PUCCH)+n_(CSI-RS)−1 totransmit a CSI-RS report or, by assigning an index “0” (instead of anindex “1”) to the first CSI-RS transmission trigger value that isdifferent than “00,” a UE with n_(CSI-RS)-th CSI-RS transmission triggervalue that is different than “00” can use PUCCH resourcen_(PUCCH)+n_(CSI-RS) to transmit a CSI-RS report. A CSI report from a UEcan a combined CSI report for each NB with triggered CSI-RS transmissionor the UE can select a predetermined number of NBs, from the NB withtriggered CSI-RS transmissions, to provide respective CSI reports.

A DL DCI format or a DCI format T can also include a TPC command fieldfor a UE to adjust a power for a transmission of a PUCCH conveying a CSIreport. A TPC command field can be next to a CSI-RS transmission triggerfield (either before or after) or can be at a different configuredlocation for each UE. A UE can be configured with more than oneCSI-RS-RNTI where the contents of DCI format T are interpreted accordingto the CSI-RS-RNTI. For example, a first CSI-RS-RNTI can correspond to afirst set of NBs or a first group of cells while a second CSI-RS-RNTIcan correspond to a second set of NBs or a second group of cells.

FIG. 27 illustrates example contents of a DCI format 2700 with CRCscrambled by a CSI-RS-RNTI that triggers CSI-RS transmissions in asubset of NBs from a set of NBs for one or more UEs according toembodiments of the present disclosure. An embodiment of the contents ofa DCI format 2700 shown in FIG. 27 is for illustration only. One or moreof the components illustrated in FIG. 27 can be implemented inspecialized circuitry configured to perform the noted functions or oneor more of the components can be implemented by one or more processorsexecuting instructions to perform the noted functions. Other embodimentsare used without departing from the scope of the present disclosure.

As shown in FIG. 27, a gNB configures to a UE a set of NBs, aCSI-RS-RNTI that scrambles a CRC of a DCI format and a location in theDCI format for a CSI-RS trigger field that triggers CSI-RS transmissionsin a subset of NBs from the set of NBs 2710. The set of NBs can beseparately configured per UE for different UEs with a same configuredCSI-RS-RNTI. The gNB determines UEs from a group of one or more UEsconfigured with a same CSI-RS-RNTI and respective subsets of NBs fortriggering CSI-RS transmissions 2720. The gNB sets values of a CSI-RStrigger field according to whether or not the gNB triggers CSI-RStransmissions for a UE 2730 and when CSI-RS transmissions are triggered,according to a subset of NBs with triggered CSI-RS transmissions.

A CSI-RS trigger field can include two bits where a value of “00” doesnot trigger any CSI-RS transmission for a UE and a value of “01,” “10”or “11” respectively triggers CSI-RS transmissions in a first, second,and third subsets of NBs that can include all NBs in the set of NBs ortriggers CSI-RS transmissions with a first, second, or thirdconfiguration in a NB indicated by a respective field in the DCI format.The gNB transmits the DCI format with CRC scrambled by the CSI-RS-RNTI2740. A UE receives from the gNB a configuration for a set of NBs, for aCSI-RS-RNTI that scrambles a CRC of a DCI format, and for a location inthe DCI format of a CSI-RS trigger field that can trigger CSI-RStransmissions in a subset of NBs 2750.

The UE detects the DCI format with CRC scrambled by the CSI-RS-RNTI2760. The UE obtains a value for the CSI-RS trigger field 2770. When thevalue of CSI-RS trigger field is “00,” the UE does not receive CSI-RSand when the value of the CSI-RS trigger field is “01,” “10” or “11,”the UE receives CSI-RS transmissions in a first, second, and thirdsubsets of NBs, respectively or receives CSI-RS according to a first,second, or third configuration 2780.

FIG. 28 illustrates example contents of a DCI format 2800 with CRCscrambled by a CSI-RS-RNTI that triggers CSI-RS transmissions in asubset of NBs from a set of NBs for one or more UEs and provides a PUCCHresource and TPC commands for transmissions of CSI reports according toembodiments of the present disclosure. An embodiment of the contents ofa DCI format 2800 shown in FIG. 28 is for illustration only. One or moreof the components illustrated in FIG. 28 can be implemented inspecialized circuitry configured to perform the noted functions or oneor more of the components can be implemented by one or more processorsexecuting instructions to perform the noted functions. Other embodimentsare used without departing from the scope of the present disclosure.

As shown in FIG. 28, a gNB configures to a UE a set of NBs, aCSI-RS-RNTI that scrambles a CRC of a DCI format and a location in theDCI format for a CSI-RS trigger field that triggers CSI-RS transmissionsin a subset of NBs from a set of NBs and a TPC command for adjusting apower of a PUCCH transmission that includes a CSI report 2810. The setof NBs can be different for different UEs. The gNB determines UEs from agroup of one or more UEs configured with a same CSI-RS-RNTI andrespective subsets of NBs for triggering CSI-RS transmissions 2820.

The gNB sets values of a CSI-RS trigger field according to whether ornot the gNB triggers CSI-RS transmissions for a UE and when CSI-RStransmissions are triggered, according to a subset of NBs with triggeredCSI-RS transmissions and a UE can process a TPC command in the DCIformat even when the UE is not triggered CSI-RS transmissions and doesnot transmit a PUCCH conveying a CSI report 2830.

A CSI-RS trigger field can include two bits where a value of “00” doesnot trigger any CSI-RS transmission for a UE and a value of “01,” “10”or “11” respectively triggers CSI-RS transmissions in a first, second,and third subsets of NBs that can include all NBs in the set of NBs.Additionally or alternatively, CSI-RS trigger field can indicate aCSI-RS configuration. The TPC command can also include two bits withvalues of “00,” “01,” “10” or “11” mapping, for example, to poweradjustments of −3 dB, −1 dB, 1 dB, and 3 dB, respectively. The gNBtransmits the DCI format with CRC scrambled by the CSI-RS-RNTI 2840.

A UE receives from the gNB a configuration for a set of NBs, for aCSI-RS-RNTI that scrambles a CRC of a DCI format, and for a location inthe DCI format of a CSI-RS trigger field that can trigger CSI-RStransmissions in a subset of NBs and the TPC field for adjusting a powerof a PUCCH that conveys a CSI report 2850. The UE detects the DCI formatwith CRC scrambled by the CSI-RS-RNTI 2860. The UE obtains a value forthe CSI-RS trigger field and for the TPC command field 2870.

When the value of CSI-RS trigger field is “00,” the UE does not receiveCSI-RS and when the value of the CSI-RS trigger field is “01,” “10” or“11,” the UE receives CSI-RS transmissions in a first, second, and thirdsubsets of NBs, or according to a first, second, or third CSI-RSconfiguration, respectively 2880. The DCI format also includes a PUCCHresource field that indicates a PUCCH resource n_(PUCCH) that is used bya UE having the first CSI-RS trigger in the DCI format with valuedifferent than “00” to transmit a PUCCH that conveys a CSI report, and aUE having the n_(CSI-RS)+1 CSI-RS trigger in the DCI format with valuedifferent than “00” used PUCCH resource n_(PUCCH)+n_(CSI-RS) to transmita PUCCH that conveys a CSI report with a power adjusted based on the TPCcommand field value 2890.

FIG. 29 illustrates an example PUCCH resource determination 2900 for aUE to transmit a PUCCH conveying a CSI report based on a PUCCH resourceindicated in a DCI format triggering CSI-RS transmissions according toembodiments of the present disclosure. An embodiment of the PUCCHresource determination 2900 shown in FIG. 29 is for illustration only.One or more of the components illustrated in FIG. 29 can be implementedin specialized circuitry configured to perform the noted functions orone or more of the components can be implemented by one or moreprocessors executing instructions to perform the noted functions. Otherembodiments are used without departing from the scope of the presentdisclosure.

Using FIG. 29 as reference, a fourth UE, UE#3 2910, having a PUCCHtransmission that conveys a CSI report in response to a detection of aDCI format that has a CRC scrambled with a CSI-RS-RNTI and includes aCSI-RS trigger field for the UE with value other than “00” and areference PUCCH resource n_(PUCCH), determines that there are two CSI-RStrigger fields, 2920 and 2930, with values other than “00” in locationsprior to a location of the CSI-RS trigger field for the UE 2940. Basedon the determination of CSI-RS trigger fields with value other than “00”in locations prior to the location of the CSI-RS trigger field for UE#3in the DCI format, UE#3 determines PUCCH resource n_(PUCCH)+2 for aPUCCH transmission that conveys a CSI report in response to measurementsfrom CSI-RS transmissions associated with CSI RS trigger value for UE#3.

A gNB can configure a UE to report CSI for M_(NB) NBs from a set ofconfigured N_(NB)≥M_(NB) NBs or a value of M_(NB) can be defined in asystem operation. The UE can select the M_(NB) NBs from the set ofN_(NB) NBs. For example, from the N_(NB) measured CQI values inrespective N_(NB) NBs, the UE can select the M_(NB)≤N_(NB) largest CQIvalues and indicate the respective M_(NB) NBs in a CSI report.

The UE can also be configured by a gNB to include a CSI report for an NBwhere the UE is configured to receive PDCCHs or inclusion of that CSIreport can be specified in the system operation. It is also possiblethat a configured set of NBs excludes an NB where a UE is configured toreceive PDCCHs and the UE can provide separate CSI reports for that NB.For example, the UE can provide CSI reports with larger periodicity forthe NB where the UE is configured to receive PDCCHs than for other NBs.

When a UE reports CSI for M_(NB)>1 NBs, the UE can report a largest CQIvalue CQI_(max)(j₀) and a respective NB index j₀ and report adifferential CQI offset value DCQI(j), with 0≤j≤M_(NB)−1 and j≠j₀, whereDCQI(j)=CQI_(max)(j₀)−CQI(j). For example, for a DCQI(j) valuerepresented by 2 bits, a mapping from the 2-bit differential CQI valueto the offset value can be as in Table 2. For N_(NB) configured NBs andM_(NB) NBs with CSI reports, indexes for the M_(NB) NBs can be obtainedusing for example a combinatorial index as in LTE specification.

A number of bits to denote a position of the M_(NB) NBs is

$\lceil {\log_{2}\begin{pmatrix}N_{NB} \\M_{NB}\end{pmatrix}} \rceil.$

Indexes of NBs can be arranged first in a CSI report followed byrespective CSI values or pairs of NB indexes and CSI reports can bearranged, for example starting from the NB with the largest CQI valueand continuing with other NBs in an ascending index order.

TABLE 2 Mapping differential CQI value to offset value Differential CQIvalue Offset value 0 ≤1 1 2 2 3 3 ≥4

An NB where a UE is configured to receive PDCCHs can hop across slotswithin a set of configured NBs. For example, an NB where a UE isconfigured to receive PDCCHs can cycle through NBs in a configured setof NBs across slots according to an ascending order of an NB index orcan have a hopping pattern maximizing frequency diversity such as an SRStransmission BW hopping pattern as described in the LTE specifications.

Then, a UE can receive PDCCHs and CSI-RS transmissions in a same NBwhile reducing an impact of a delay associated with returning from afirst NB where the UE is configured to receive PDCCHs to a second NB toreceive CSI-RS transmissions, and then back to the first NB to receivePDCCHs. This can be particularly useful when a retuning time betweendifferent NBs is relatively large and a UE cannot receive CSI-RStransmissions for all respective NBs in a single slot.

When a UE is not configured reception of a PDSCH or of other DLsignaling in a slot, the UE can use a remaining duration in the slot,after the symbols where the UE decodes PDSCHs and a few one or moreadditional symbols associated with a processing delay to determinepotential scheduling of PDSCHs, for retuning to a different NB forreception of PDCCHs and possibly of CSI-RS.

When a UE is configured reception of a PDSCH or of other DL signaling ina slot and the UE does not have sufficient time to retune to a next NB,according to the NB hopping pattern, prior to the beginning of a nextslot then, as is subsequently discussed, the UE can either skip retuningto a next NB and reestablish the NB hopping pattern at a later slot orthe UE can retune to the next NB but miss reception of PDCCHs due toretuning. To mitigate the impact of an inability to receive PDCCHs in aslot, a gNB can schedule a multi-slot transmission of a PDSCH to a UEwhere the PDSCH is transmitted within different NB s in different slotsaccording to an NB hopping pattern. Then, when a UE can retune within atime period that is not larger than a configured duration fortransmissions of PDCCHs in a slot, the UE can receive the PDSCH afterreturning to different NB s in different slots.

FIG. 30 illustrates a hopping pattern 3000 of an NB that a UE isconfigured to receive PDCCHs according to embodiments of the presentdisclosure. An embodiment of the hopping pattern 3000 shown in FIG. 30is for illustration only. One or more of the components illustrated inFIG. 30 can be implemented in specialized circuitry configured toperform the noted functions or one or more of the components can beimplemented by one or more processors executing instructions to performthe noted functions. Other embodiments are used without departing fromthe scope of the present disclosure.

As shown in FIG. 30, a UE is configured a set of NBs that includes fourNBs, NB0, NB1, NB2, and NB3, and resources in first symbol of an NB forreception of PDCCHs 3005. In a first slot, the UE receives PDCCHs in NB13010 and can also receive CSI-RS transmissions in slot symbols withfirst time distance to the end of the first slot that is larger than aUE retuning period. The UE is not configured to receive any DL signalingduring a time period equal to the retuning period relative to the end ofthe first slot.

During the first time distance, the UE can retune to NB3 for receptionof PDCCHs in a second slot. In the second slot, the UE receives PDCCHsin NB3 3020 and can also receive CSI-RS transmissions in slot symbolswith second time distance to the end of the second slot that is largerthan a UE retuning period. The UE is not configured to receive other DLsignaling during a time period equal to the retuning period relative tothe end of the second slot. During the second time distance, the UE canretune to NB0 for reception of PDCCHs in a third slot. In the thirdslot, the UE receives PDCCHs in NB0 3030 and can also receive CSI-RStransmissions in slot symbols with third time distance to the end of thethird slot that is larger than a UE retuning period.

The UE is not configured to receive any DL signaling during a timeperiod equal to the retuning period relative to the end of the thirdslot. During the third time distance, the UE can retune to NB2 forreception of PDCCHs in a fourth slot. In the fourth slot, the UEreceives PDCCHs in NB2 3040 and can also receive CSI-RS transmissions inslot symbols with fourth time distance to the end of the fourth slotthat is larger than a UE retuning period.

The UE is not configured to receive any DL signaling during a timeperiod equal to the retuning period relative to the end of the fourthslot. During the fourth time distance, the UE can retune to NB1 forreception of PDCCHs in a fifth slot. In the fifth slot, the UE receivesPDCCHs in NB1 3050, can also receive CSI-RS transmissions in slotsymbols, and is configured to receive DL signaling, such as a PDSCH,with fifth time distance to the end of the fifth slot that is not largerthan a UE retuning period. The UE does not have enough time to retune toNB3 for reception of PDCCHs in a sixth slot while receiving the DLsignaling in the fifth slot and there are two approaches for the UEbehavior.

A first approach is for the UE to retune to NB3 in the sixth slot forpossible reception of CSI-RS transmission but without the UE being ableto receive PDCCHs 3060. A second approach is for the UE to remain tunedto NB1 in the sixth slot to receive PDCCHs in the sixth slot 3065. Thefirst approach avoids error cases that can occur for example when the UEfails to detect a DL DCI format in the fifth slot scheduling a DL datachannel reception in the fifth slot and retunes to NB3 in the sixthslot.

The second approach relies on the gNB to account for potential errorcases. Both approaches can enable continuous scheduling for a UE; thefirst approach by applying multi-slot scheduling and relying on the UEto retune within a time period for transmission of DL control channelsin a slot, the second approach by applying either single-slot ormulti-slot scheduling for the UE. The UE resumes the NB hopping patternin a seventh slot 3070. The UE behavior can be specified in a systemoperation or configured to the UE by the gNB according to one of the twoapproaches.

An SRS transmission over multiple NBs can follow similar principles asCSI-RS transmission over multiple NBs and the following descriptions aresummarized for completeness. SRS transmissions in NBs can be precoded ornon-precoded. In the former case, a precoding can also be configured toa UE and can be same for all NBs (single configuration) or different fordifferent NBs (separate configuration). SRS transmissions can includezero-power SRS and non-zero-power SRS.

In order for a UE to transmit SRS in NBs from a set of NBs, the UE needsto retune the UE's RF transmitter components to each of the NBs from theset of NBs. When the UE is configured to transmit UL signaling such as arandom access channel, or a PUSCH, or a PUCCH such as one conveyingHARQ-ACK in an NB and the UE is also configured to transmit SRS in adifferent NB and an RF retuning delay is such that the UE cannottransmit the UL signaling and the SRS, the UE can drop the SRStransmission.

For a TDD system and a UE with a single duplexer, when a retuning delayis smaller than a time interval between a last slot symbol where the UEis configured to receive PDCCHs in a first NB and a first slot symbol ofan SRS transmission in a second NB, the UE can transmit SRS in thesecond NB after receiving PDCCHs in the first NB. When a retuning delayis smaller than a time interval between a last slot symbol fortransmitting SRS in the second NB and a first slot symbol for receivingPDCCHs in the first NB, the UE can retune to the first NB to receivePDCCHs after transmitting SRS in the second NB.

When the UE detects a DCI format in a PDCCH that schedules the UE toreceive a PDSCH or PUSCH in an NB and the UE is also configured totransmit SRS in a different NB, the UE can drop transmission of the SRS.For a TDD system and a UE with a single duplexer, when a retuning delayis larger than a time between a last symbol of a PDSCH reception or aPUSCH transmission and a first symbol of an SRS transmission (or thereverse), the UE can drop the SRS transmission.

In one example, SRS transmission in a set of one or more NBs can besemi-persistent or periodic. A UE is configured by higher layers the setof NBs and parameters for SRS transmission in each NB from the set NBs.SRS transmission parameters can be same for all NBs, except possibly alocation of slot symbols for SRS transmissions as it is furtherdiscussed in the following, and can be jointly configured for all NBs orsome can be different per NB and be separately configured for each NB.SRS transmission parameters can include one or more of a number ofcombs, a number of slot symbols (duration) for SRS transmission in eachNB, a transmission comb, a starting PRB, a periodicity, a BW, a cyclicshift, a precoding, or a number of antenna ports.

In another example, SRS transmission in a set of NBs can be aperiodicand triggered by a DCI format conveyed by a PDCCH. The DCI format can bea DL DCI format scheduling a PDSCH transmission to a UE, or an UL DCIformat scheduling a PUSCH transmission from a UE, or a separate DCIformat with contents triggering SRS transmissions from one or more UEs.

When a DCI format triggering SRS transmissions in one or more NBs from aset of NBs is an UL DCI format or a DL DCI format, the DCI format caninclude a field indicating NBs from the configured set of NBs forrespective SRS transmissions from a UE, or can include a fieldindicating a SRS transmission configuration, in a similar manner asdescribed for triggering of CSI-RS transmissions. For an UL DCI formatthat schedules a transmission of a PUSCH from a UE and triggers SRStransmissions in NBs from a set of NBs from the UE, when an NB of thePUSCH transmission is also an NB with triggered SRS transmission then,in order to be able to transmit the PUSCH, the UE can expect that afirst SRS transmission occurs in the NB of the PUSCH transmission andsubsequent SRS transmissions are in remaining NBs according to anascending (or descending) order of an NB index.

When an NB of a PUSCH transmission is not an NB with a triggered SRStransmission, the UE can transmit the PUSCH in the one or more slots andsubsequently, after the one or more slots, retune to NBs with triggeredSRS transmission. It is also possible that SRS transmissions in NBs areaccording to an ascending NB index including, when an SRS transmissionis triggered, an NB of a PUSCH transmission.

A field in an UL DCI format triggering SRS transmission in one or moreNBs from a set of NBs that a UE is configured can include an indicationof the NBs. For example, a field with two bits can indicate no SRStransmissions using a “00” value, and indicate SRS transmission in afirst, second, or third configured sub-sets of NBs from the set of NBsusing a “01,” a “10” and a “11” value, or indicate a first, second, orthird configuration for a SRS transmission, respectively. Parameters forSRS transmission in each NB can be same or different.

A location of slot symbols for SRS transmission in each NB can be sameor different. For example, when SRS transmission is in different slotsin respective different NBs, respective slot symbols can be same. Forexample, when SRS transmission in at least some NBs are in a same slot,respective slot symbols are different and a respective offset in numberof symbols for successive SRS transmissions can be determined from aretuning delay for UEs with associated triggered SRS transmissions orcan be signaled by a gNB either by UE-common higher layer signaling,such as system information, or by UE-specific higher layer signaling.

An SRS transmission in an NB can also be over multiple slot symbolswhere, for example, SRS transmission is from different antenna ports indifferent symbols, such as from a first antenna port in a first symboland a second antenna port in a second symbol, or from same antenna portsin order to enable a gNB to obtain a more accurate estimate of a channelmedium from the SRS transmission.

When a DCI format triggering SRS transmissions in NBs from a set of NBsfor a UE is not an UL DCI format or a DL DCI format, the DCI format canhave a same size as an UL DCI format or a DL DCI format that the UEdecodes, or as a size of a DCI format that the UE decodes for otherpurposes such as for obtaining TPC commands. A CRC of the DCI format canbe scrambled with an RNTI specific to triggering of SRS transmissionssuch as an SRS-RNTI. A DCI format with an SRS-RNTI is referred to forbrevity as DCI format X.

Using a DCI format X, a gNB can trigger SRS transmissions in differentNBs from a configured set of NBs, and possibly also in different cells,for each UE from a group of UEs configured with a same SRS-RNTI. A UEcan be configured a location in DCI format X through an index aparameter Index-SRS where the UE can obtain an SRS trigger fieldindicating SRS transmissions in a subset of NBs from the configured setof NBs or indicating a SRS transmission configuration. The SRS triggerfield can operate as described for an UL DCI format or a DL DCI formator can have increased granularity similar to CSI-RS triggering.

It is also possible that, when an SRS trigger field triggers SRStransmissions, it does so for all NBs in the set of NBs. Then, the SRStrigger field can include a single bit for each UE per cell where avalue of “0” indicates no SRS triggering and a value of “1” indicatesSRS triggering in all NBs in the set of NBs. A DL DCI format or a DCIformat X can also include a TPC field for a UE to adjust an SRStransmission power. A TPC command field can be next to an SRStransmission trigger field (either before or after) or can be at adifferent configured location for each UE. A UE can be configured withmore than one SRS-RNTI where the contents of DCI format X areinterpreted according to the SRS-RNTI. For example, a first SRS-RNTI cancorrespond to a first set of NBs or a first group of cells while asecond SRS-RNTI can correspond to a second set of NBs or a second groupof cells.

The functionalities of a DCI format T and a DCI format X can be combinedusing a DCI format Y that can have a same size as an UL DCI format or aDL DCI format that the UE decodes, or as a size of a DCI format that theUE decodes for other purposes such as for obtaining TPC commands. A UEcan be configured with an RS-RNTI for triggering both CSI-RStransmissions and SRS transmissions and with one or more respectivelocations, for respective one or more cells, for a CSI-RS trigger field,followed by an SRS trigger field, and followed by a TPC command field(or in any other order for these three fields) where a cell for CSI-RSreception can be different than a cell for SRS transmission and a linkbetween cell index and trigger location is separately configured. DCIformat Y can also include a reference PUCCH resource for PUCCHtransmissions in response to CSI-RS trigger values other than “00” asdescribed in FIG. 29.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

None of the description in this application should be read as implyingthat any particular element, step, or function is an essential elementthat must be included in the claims scope. The scope of patented subjectmatter is defined only by the claims. Moreover, none of the claims areintended to invoke 35 U.S.C. § 112(f) unless the exact words “means for”are followed by a participle.

What is claimed is:
 1. A method for a user equipment (UE) for receivinga physical downlink control channel (PDCCH), the method comprising:receiving configuration information for a first control resource setthat includes a number of symbols in a time domain and a number ofresource blocks (RBs) in a frequency domain; receiving configurationinformation indicating a first number N_(bundle,1) offrequency-contiguous RBs; and receiving a first PDCCH in the firstcontrol resource set in a number of frequency distributed blocks ofN_(bundle,1) RBs, wherein a demodulation reference signal associatedwith the reception of the first PDCCH is assumed to have a sameprecoding over the N_(bundle,1) RBs.
 2. The method of claim 1, furthercomprising: receiving configuration information for a second controlresource set that includes a number of symbols in the time domain and anumber of RBs in the frequency domain; receiving configurationinformation indicating a second number N_(bundle,2) offrequency-contiguous RBs; and receiving a second PDCCH in the secondcontrol resource set in a number of frequency contiguous blocks ofN_(bundle,2) RBs, wherein a demodulation reference signal associatedwith the reception of the second PDCCH is assumed to have a sameprecoding over the N_(bundle,2) RBs.
 3. The method of claim 1, furthercomprising receiving configuration information indicating use of a sameprecoder for the demodulation reference signal associated with thereception of the first PDCCH over all RBs of the first control resourceset.
 4. The method of claim 1, further comprising: receivingconfiguration information for a third control resource set that includesa number of symbols in the time domain and a number of RBs in thefrequency domain; and receiving a third PDCCH that schedules receptionof a first system information block in the third control resource set ina number of frequency distributed blocks of a predetermined number ofRBs, wherein a demodulation reference signal associated with thereception of the third PDCCH is assumed to have a same precoding overthe predetermined number of RBs.
 5. The method of claim 1, furthercomprising: receiving configuration information for a first search spaceto receive a PDCCH in the first control resource set during first timeoccasions; and receiving configuration information for a second searchspace to receive a PDCCH in the first control resource set during secondtime occasions.
 6. The method of claim 1, wherein: the first PDCCHprovides a UE-specific downlink control information (DCI) format; thedemodulation reference signal associated with the reception of the firstPDCCH is scrambled by a first sequence when the first PDCCH is receivedin a common search space; and the demodulation reference signalassociated with the reception of the first PDCCH is scrambled with asecond sequence when the first PDCCH is received in a UE-specific searchspace.
 7. The method of claim 1, wherein: the first control resource setincludes N_(control) ^(set) symbols, N_(control) ^(set) RBs from theN_(bundle) of RBs are located sequentially on a first RB overN_(control) ^(set) symbols, and next N_(control) ^(set) RBs from theN_(bundle) of RBs are located sequentially on a second RB overN_(control) ^(set) symbols, and an index of the second RB is larger byone relative to an index of the first RB.
 8. A user equipment (UE)comprising: a receiver configured to receive: configuration informationfor a first control resource set that includes a number of symbols in atime domain and a number of resource blocks (RBs) in a frequency domain;configuration information indicating a first number N_(bundle) offrequency-contiguous RBs; and a first physical downlink control channel(PDCCH) in the first control resource set in a number of frequencydistributed blocks of N_(bundle) RBs, wherein a demodulation referencesignal associated with the reception of the first PDCCH is assumed tohave a same precoding over the N_(bundle,1) RBs.
 9. The UE of claim 8,wherein the receiver is further configured to receive: configurationinformation for a second control resource set that includes a number ofsymbols in the time domain and a number of RBs in the frequency domain;configuration information indicating a second number N_(bundle,2) offrequency-contiguous RBs; and a second PDCCH in the second controlresource set in a number of frequency contiguous blocks of N_(bundle,2)RBs, wherein a demodulation reference signal associated with thereception of the second PDCCH is assumed to have a same precoding overthe N_(bundle,2) RBs.
 10. The UE of claim 8, wherein the receiver isfurther configured to receive configuration information indicating useof a same precoder for the demodulation reference signal associated withthe reception of the first PDCCH over all RBs of the first controlresource set.
 11. The UE of claim 8, wherein the receiver is furtherconfigured to receive: configuration information for a third controlresource set that includes a number of symbols in the time domain and anumber of resource blocks RBs in the frequency domain; and a third PDCCHthat schedules reception of a first system information block in thethird control resource set in a number of frequency distributed blocksof a predetermined number of RBs, wherein a demodulation referencesignal associated with the reception of the third PDCCH is assumed tohave a same precoding over the predetermined number of RBs.
 12. The UEof claim 8, wherein the receiver is further configured to receive:configuration information for a first search space to receive a PDCCH inthe first control resource set during first time occasions; andconfiguration information for a second search space to receive a PDCCHin the first control resource set during second time occasions.
 13. TheUE of claim 8, wherein: the first PDCCH provides a UE-specific downlinkcontrol information (DCI) format; the demodulation reference signalassociated with the reception of the first PDCCH is scrambled by a firstsequence when the first PDCCH is received in a common search space; andthe demodulation reference signal associated with the reception of thefirst PDCCH is scrambled with a second sequence when the first PDCCH isreceived in a UE-specific search space.
 14. The UE of claim 8, wherein:the first control resource set includes N_(control) ^(set) symbols,N_(control) ^(set) RBs from the N_(bundle) of RBs are locatedsequentially on a first RB over N_(control) ^(set) symbols, and nextN_(control) ^(set) RBs from the N_(bundle) of RBs are locatedsequentially on a second RB over N_(control) ^(set) symbols, and anindex of the second RB is larger by one relative to an index of thefirst RB.
 15. A base station (BS) comprising: a transmitter configuredto transmit: configuration information for a first control resource setthat includes a number of symbols in a time domain and a number ofresource blocks (RBs) in a frequency domain configuration informationindicating a first number N_(bundle) of frequency-contiguous RBs; and afirst physical downlink control channel (PDCCH) in the first controlresource set in a number of frequency distributed blocks of N_(bundle)RBs, wherein a demodulation reference signal associated with thetransmission of the first PDCCH is assumed to have a same precoding overthe N_(bundle,1) RBs.
 16. The base station of claim 15, wherein thetransmitter is further configured to transmit: configuration informationfor a second control resource set that includes a number of symbols inthe time domain and a number of RBs in the frequency domain;configuration information indicating a second number N_(bundle,2) offrequency-contiguous RBs; and a second PDCCH in the second controlresource set in a number of frequency contiguous blocks of N_(bundle,2)RBs, wherein a demodulation reference signal associated with thereception of the second PDCCH is assumed to have a same precoding overthe N_(bundle,2) RBs.
 17. The base of claim 15, wherein the transmitteris further configured to transmit a configuration information indicatinguse of a same precoder for the demodulation reference signal associatedwith the transmission of the first PDCCH over all RBs of the firstcontrol resource set.
 18. The base station of claim 15, wherein thetransmitter is further configured to transmit: configuration informationfor a third control resource set that includes a number of symbols inthe time domain and a number of RBs in the frequency domain; and a thirdPDCCH that schedules reception of a first system information block inthe third control resource set in a number of frequency distributedblocks of a predetermined number of RBs, wherein a demodulationreference signal associated with the reception of the third PDCCH isassumed to have a same precoding over the predetermined number of RBs.19. The base station of claim 15, wherein the transmitter is furtherconfigured to transmit: configuration information for a first searchspace for a PDCCH transmissions in the first control resource set duringfirst time occasions; and configuration information for a second searchspace for a PDCCH transmissions in the first control resource set duringsecond time occasions.
 20. The base of claim 15, wherein: the firstcontrol resource set includes N_(control) ^(set) symbols, N_(control)^(set) RBs from the N_(bundle) of RBs are located sequentially on afirst RB over N_(control) ^(set) symbols, and next N_(control) ^(set)RBs from the N_(bundle) of RBs are located sequentially on a second RBover N_(control) ^(set) symbols, and an index of the second RB is largerby one relative to an index of the first RB.